I believe it is by Crazy Wolfgang, one of the traveling merchants. After investing a total of 700 caps into his business through Uncle Roe in the Canterberry Commons, he can repair your gear up to 85%.
If you have a high repair skill, and want to get it repaired for free(probably considered cheating), press the tilda key (~), its under the ESC key, to open up the console while in game and type this, but without the quotes "player.srm" to open up a repair menu for yourself. It allows you to repair your own gear as if you were a merchant, so you don't need any parts. Also, although it says it is still costing you money, remember, you are paying yourself.