I'd recommend emulation, but nothing compares with the feel of an NES Controller in your palms. So, how about a USB NES Controller?
http://www.phreque.com/index.php?pag...hk=1&Itemid=19
This is just a suggestion, not an endorsement of emulation or any form of piracy. I gather that since you want a collection you probably want the physical cartridges anyway. If I come across any of mine I'm willing to part with, I will let you know.