Hey guys sorry for bringing back [my own] old post but I realized I never updated when I ran across this in a search...
The 5mm UV LED's I had (harvested out of a kids toy) worked perfectly in the AAA C8's I got from DX. Ran them on NiMH's and Energizer L91's. They worked amazingly well for checking bills which is all I wanted them for anyway. At the first gun show I did with them the guy in the booth next to me asked where I got them so I sold him one for $6 (originally paid $12 for all 3), of the two remaining one got lost (possible stolen from my booth) and then a week later the final one took a swim in a cooler of ice water on the come-to-you lunch cart the guy felt so bad (it wasn't at all his fault) that he gave us the food for free so I told him to take the light and if it worked after drying out he could keep it and told him it was a bill checker. All in all a big success and if I can acquire some more 5mm UV emitters I'll probably place an order for 3 more mini C8's to do the same thing with again.
yep simply replaced the emitter, nothing else. Not sure if it'd hold up to being switched on for any length of time but the forward clickies in these worked great for momentary use, it only takes two seconds to check a bill (shined it from the back of the bill and looked for the strip).