The easiest ways to do this involve...
By taking a 2-level dip into Fighter, any character has access to Action Surge:
Starting at 2nd level, You can push yourself beyond your normal limits for a moment. On your turn, you can take one additional action on top of your regular action and a possible bonus action.
So, once per short rest, you can take a second action to accomplish your goal. This is still a pretty steep cost to get a single throwable item off in one round, but sometimes masters of the arcane arts have reasons beyond our comprehension!
Combinations that allow this include using Action Surge to throw the item after:
- The aforementioned Conjuration Wizard method, based on the ability "Minor Conjuration" [Requires Wizard 2, School of Conjuration]
Starting at 2nd level when you select this school, you can use your action to conjure up an inanimate object in your hand or on the ground in an unoccupied space that you can see within 10 feet of you. This object can be no larger than 3 feet on a side and weigh no more than 10 pounds, and its form must be that of a nonmagical object that you have seen. The object is visibly magical, radiating dim light out to 5 feet. The object disappears after 1 hour, when you use this feature again, or if it takes any damage.
- Using Wish to replicate the effects of Creation [Fifth-level spell] as an action, as you described. Note that doing this doesn't run the risk of losing Wish forever, since it's replicating a lower-level spell's effect.
You pull wisps of shadow material from the Shadowfell to create a nonliving object of vegetable matter within range: 50ft goods. rope, wood, or something similar. You can also use this spell to create mineral objects such as stone, crystal, or metal. The object created must be no larger than a 5-foot cube, and the object must be of a form and material that you have seen before.
- Using Wish [Ninth-level spell] to create the object, which carries the 1-in-3 chance to never be able to cast that spell again
I started to include a method of the Illusion School with Illusory Reality, but that explicitly states the object cannot deal damage or directly harm anyone. Although I guess you could get their attention with it...
By 14th level, you have learned the secret of weaving shadow magic into your illusions to give them a semireality. When you cast an illusion spell of 1st level or higher, you can choose one inanimate, nonmagical object that is part of the illusion and make that object real. You can do this on your turn as a bonus action while the spell is ongoing. The object remains real for 1 minute. For example, you can create an illusion of a bridge over a chasm and then make it real long enough for your allies to cross. The object can't deal damage or otherwise directly harm anyone.
Abilities that allow you to summon actual weapons
Two options are out there, with slightly different traits:
- Eldritch Knights can bond with up to two weapons, allowing them to recall the weapon as a Bonus Action:
Once you have bonded a weapon to yourself, you can't be disarmed of that weapon unless you are incapacitated. If It is on the same plane of existence, you can summon that weapon as a bonus action on your turn, causing it to teleport instantly to your hand.
Emphasis mine. So if you bond with a dagger and leave it anywhere on your plane of existence, then you can walk naked and unarmed into a room, call it to your hand as a Bonus Action, and throw it with an Attack Action. No spells needed, and all it takes is three levels of fighter.
I admit this is not the same as creating a weapon to throw, but it could be functionally the same, depending on WHY you need to summon throwing knives. Plus, this can be redone every turn so long as the weapon remain in tact.
- Three levels of Warlock will let you summon Pact Weapons:
You can use your action to create a pact weapon in your empty hand. You can choose the form that this melee weapon takes each time you create it...This weapon counts as magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage.
Again, this requires two levels of Fighter to Action Surge after the creation so you can throw it on the same turn, but this doesn't require bonding with a weapon in advance. of course, it requires "striking a bargain with an otherworldly patron," but let's not nitpick.