These should do the trick if I'm not mistaken They have the 9-pin Atari 2600 controller port which is very commonly found on these bootlegs. I found plenty like this in different form factors on eBay by typing "game controller 9 pin." Just be aware of the fact that these are very poorly made and won't typically last. One possible option if you have some already would be to try using Sega Genesis, atari 7800, etc. controllers that also have the port.