Where do I find more of these? I have a lot of good weapons (assault carbine, tons of energy weapons, and unique ones) but I never use them because it costs a fortune to repair! Also is there any way to repair my armor for free or cheaper?

I've only gotten two. That was for helping the NCR out at the Mojave Outpost, but I do believe you can make them. I'm not so sure, so why don't you go check next time you play? As for cheaper repairing, you either have to have a higher Barter skill or do it yourself. Also I think Raul(Companion) can repair stuff for you also.

Thanks. Definitely going to have to look for this Raul companion.

I just got raul. He doesn't repair weapons but having him in your party makes weapon and armor degrade slower.

Trying going to his shack. You can repair some stuff their I think

in F:NV you can repair your own stuff up to 100% regardless of your repair skill. You don't need a repair kit, just find a duplicate of the weapon you want to repair.

If your repair skill is high enough, I think you gain the ability to repair using other weapons that are similar but not exactly the same type

They're apparently sold in Nellis (at the munitions store), and are occasionally carried by Legion members. You can also craft them but they require 5 different ingredients.

There are some pre-placed ones throughout the game, but not in a quantity enough to be worth seeking them out, probably.