Is there a spell I can use to create a bedroll each night? A magic item would be suitable as well. The spell should be of a low level, i.e. 1 or 2.
There aren't many things that fit your criteria--either a low-level spell that creates a comfy thing to sleep on or a magic item that makes a comfy thing to sleep on that's appropriate for a level 4 character. Nonetheless, here's
One Spell and Two Items
- The 2nd-level Sor/Wiz spell Leomund's tiny igloo [conj] (Fr 101) for 2 hours/level creates an igloo for Medium you and 3 Medium friends. Its walls have hardness 0 and 3 hp per caster level, it withstands up to (but not including) hurricane winds, and its magically heated. It's very cool.1
- The slotless item survival pouch (MIC 187-8) (3,300 gp; 5 lbs.) grants the possessor the ability as a standard action 5/day to pull from it a variety of things, including a tent and 2 bedrolls as but 1 of its 5 uses per day. Other items include a lit campfire and a summoned-like decked-out mule (although it won't fight for you).
- The slotless item Heward's fortifying bedroll (CM 132-3) (3,000 gp; 2 lbs.) grants the user the ability to get 8 hours rest in just 1 hour.
Both items are expensive for a lone level 4 character, but splitting the cost among party members makes either more palatable. The pouch is extremely versatile, and if your party's permanently camping it should provide everything your party needs in a 5 lb. package. And while it's a little gross taking shifts sleeping in the same fortifying bedroll, it's only an hour--just use the spell prestidigitation afterward to clean off leftover barbarian lice.2 The advantage of shorter watches with more people on them is huge.
- The lice are from the barbarian not actual barbarians.
- Have a minion. Carrying things is for dweebs - the wizard on the go has a little skeleton buddy (Necromancer alternate class feature from UA), a hired minion, or a Fighter to lug his stuff for him.
- Tenser's Floating Disk, or a Talisman of the Disk, can handle your 'carrying stuff' problem, admittedly though only for a couple of hours at low levels.
- Prestidigitation, the wonder-cantrip, can clean things and create a few pounds of soft material. Grab some grass or dirt, clean it until it's soft, and then manifest a pillow.
- Spell Research! Summon Bedroll sounds like a 1st or 2nd level spell to me, and custom spell research is Core! (DM Fiat, though)
- Endure Elements makes wrapping yourself up in your fancy cloak (all wizards have fancy cloaks) and sleeping the night much less of a hassle!
At higher levels, a portable hole with a bedroom-cum-lab slotted into it is fine diddly dandy, as is a Mordenkainen's Magnificent Mansion. But yeah, at lower levels, you're basically gonna have to rough it. There's not even an easy magical way to sling a hammock, until you start hitting the mid-ranges where it's easier just to teleport home.
Leomund's Secure Shelter will do you one better, by conjuring a whole cottage. Not a very large cottage, mind you (that's what Mordenkainen's Magnificent Mansion is for), but it'll get the job done, and it comes with basic furnishings. The main drawback is that it's a fourth-level spell.
If you're willing to be a bit more flexible, you could also get by with Leomund's Tiny Hut. It's only 3rd level, and it actually provides better protection from the elements: the Shelter has to be heated and cooled like any ordinary house would, while the Hut does not. On the other hand, the Hut doesn't come furnished, so you'd still need to either bring a bedroll or forage for something a little softer than the ground. It also won't protect you from attacks like the Shelter can. But if your main concern is making camping as little work as possible, it's probably a better option.
One of my DMs recently let me research the process of making an "instant yurt" that could set itself up on demand, and pack itself up into a small pouch for easy portability: sort of like a folding boat except with a large, comfortable tent. I used Leomund's Tiny Hut as the principal spell in the process. It actually worked out quite well.
Some spells to summon items:
A conjuration spells to make the item:
Some other good standbys:
Finally, you can get into epic spells, and use the conjure spell seed
You could finally try and convince the DM to allow you to make a spell for specifically summoning/conjuring a bedroll.
Sadly, it looks like conjuring useful items like this just isn't accessible to low-level wizards.
You say you need a sleeping mat? Well, you'd have to wake up thrice to get your 9 hours of sleep (the amount you've stated in your comment), but as a very non-RAW solution, I'd say casting Mage Armor could be a solution. :D
It's a first level spell, so you can cast it. The rules say it's a tangible field of force, so it would keep you away from both the ground and minor creatures. Its description also states that it entails no speed reduction and no armor penalty at all - so it's probably not too tough either. And it keeps you protected as well. All you have to do, again, is to renew it thrice during the night. And waste three good spells... (I dare suppose your wizard has some bonus spells?)
Note: Don't take this answer too seriously, please. (Even though it could work. At least in my campaigns, for a mage foolish enough to do this.) :D