i know of guy who not only convert legit super famicom and snes controller to USB he rebuilds them and test them him self. and i don't mean he cleans them, i mean this guy must using a feeler gauge and measuring down to the thousands even my picky friend was jaw dropped when got this thing in, hell we though it was fake re pop until we found a few wear marks on the nintendo stamp on the back. man the buttons were TIGHT.
Sure i'm talking it up a little but look at the guy's feedback, http://www.ebay.com/usr/00hondasilverex?_trks … 788.m1543.l2754 read the comments they left. even if it isn't the most perfect controller my friend REALLY liked it and, the controller weren't sloppy, it wasn't to faded (retro bright or bleached or something) and it look professionally done, nice and neat.
sure you can use and original but, might consider the fact this guy goes through the whole controller and puts in the best condition parts and play test them him self.... or he used to. you might have to send him a message and ask if he will make you one.