Handling merchant inventory with lots of items?

Question

Ok, so I'm converting a roguelike video game to a tabletop game (GearHead, if anyone's interested), and I'm running into a catch where I want to keep the tabletop game essentially compatible with the video game, at least in terms of feel and play, but I'm having issues with some stuff.

Namely, right now, I'm struggling with handling gear availability. I want to basically be able to import the original game's gear list verbatim (which is a mechanics difficulty), but I also want to keep stuff from coming up too often- a mecha may be common enough to buy on a regular basis, but how often can you walk into a store and buy a Vadel (luxury combat mecha)? Not often.

So the question is how can I make this system flexible enough for it not to require gear lists (and potentially automatically preclude characters getting what they want), allow for local vendor density (certain places have no gun control and open weapon markets, others are hesitant to sell you a pointy stick), and also keep the original game's feel where you just walk up to a vendor and he tells you "Look at this!".

Also, does anyone know of a simple system to suggest similar items if the original roll fails? "I don't have a laser axe, but here's a survival knife!" that is somewhat dynamic? Should I just make a table with various types of items, and whenever someone shops for a certain type of weapon (the game itself tags items as being [MELEE] or [L5] depending on stuff like where they're found or how they're used), just roll on that table if they fail?

The way the original game works is that you approach, say, a weapon vendor, and he has a list of maybe four or five general [ADVENTURE] items, a dozen or so [WEAPON] items, and maybe a [ARMOR] or [MECHA] for sale, and if you don't like it you wait or go to another vendor, since his items are restocked every in-game day.

EDIT: Ok, what I've worked out as a potential system is this:

A shopping roll is used based on the relative value of the item and whether or not it's carried by the shops in an area normally. If it succeeds, the desired item is found. The scale of this will be exponential; something costing $100 will be a difficulty category lower than something costing $1000, and something that is not sold in an area will be two difficulty categories higher than the other (I need to actually analyze the dice used to define difficulty categories).

Should this roll fail, there's a second roll that is less difficult and is based on rarity. This is just modified by the difficulty category, and the random number generated will be biased towards a cheaper item (the tables it is rolled on have primarily low-cost items and a handful of entries for high-cost items).

Alternatively, I've been contemplating having failure mean that a broken (the system tracks durability) version of the item is available at a higher than normal price, meaning that repairs and the item itself are expensive and prohibitive. The downside of this is that setting a permanent durability cap, while probably a good idea if I were to follow this path, is outside the scope of the normal game, and could really tick players off or just be a non-issue (permanently decreased armor would be horrible, while a permanently damaged grenade is as good as a normal grenade); this means that I would need to create different rules for different types of items, which makes sense on some levels but also makes the game more complicated (the rules come to 9 pages when moved from my site to a word processor, though proper formatting would decrease this a good deal), and it's already looking to be a nightmare for combat (but actually incredibly stellar for out-of-combat stuff, in my probably biased).

I've also been contemplating going the "mail-order" route like I do for my Shadowrun group where I just say "roll [appropriate shopping skill] and see if you get it", with cost and time being modified by failure or success. The downside of this is that it both means that there's no potential for sales (which occur in the original game) and it also simplifies a wonderful system that sets up a great flavor.

The final alternative is to just roll off of tables every time the players go to a shop, which is simple and quick, but means that it's a lot of rolling at once (or requires the same amount of time in preparation) and is entirely hit-or-miss, sort of how the game currently handles it, but the game offers something like a dozen of these within each area, so searching for a specific type of item or even something in a particularly small category of items is practically impossible.

Answer 1

Here's the system I've sort of stumbled on:

Shopping functions with a target number based on how common the tag for an item is: difficulty to find a specific item starts at "medium", whatever I calculate that as being in the end (skill+stat rating of ~8 would be pretty average, and rolls 2d10), so on account of that I'd estimate that medium should be about 11, and the difficulty per level would be 3, so for every decimal place past the fourth the number goes up by 3 (Asking about something that costs $1,000,000 would require a roll of 20, nigh impossible with a skill rating of 8).

Should this roll fail, the player rolls on a table related to the gear type, i.e. weapon, and then gets the option of buying a similar weapon.

The issue would be limiting the number of shopping rolls, achieved by allowing each player to ask for only 3 pieces of gear per visit to a shopping center, allowing particularly skilled shoppers to try to get stuff for their buddies.

EDIT: One thing I forgot to point out is that dice explode, meaning that a difficulty of 11 is more doable.

Answer 2

At the table handling the large lists would be difficult to do without computer support.

You may want to look at d20 modern's wealth system. Items are given a flat DC value to purchase that you can modify as the situation requires (location, legality, etc). Then the player's roll against the DC to see if they can afford it. In my game I treat the roll as market variations. So I would create a website or excel doc that you plug in the wealth rank of the merchant and whatever modifiers then hit go. The program would then automatically roll against the master table and spit out a list of things the merchant succeeded at.

At leas that is how I would do it programmatically, and other then generating sheets upon sheets of random lists before game and just have them at hand to draw a random one as needed, that is the only way I could see doing this.