The only easy way I could think of would be a Neo Geo to PS2 adapter plugged into a PS2 to USB adapter, however I highly doubt this would work since most USB controllers won't work with it. I was looking into making one however I can't afford the time for something that I'd only want as a proof of concept item. I don't think it would be that hard though, there is a guy on here that sells the extension cords, who can get you cables with just one end and most of the rest you can likely get from electronic stores like MCM or maybe even Radio Shack. You could always sacrifice a stick to make an adapter if you don't want to look up how to build your own board but that's not as fun.
In reply to comments 19-20, 22-23: I completely disassembled one and posted my findings in post 16. I outlined what I believe to be the source of the issue and different ways to fix it. I still maintain that for 50 US Dollars this is not a bad stick by any means. To all of those who complain I would like to know which $50 or close sticks they are comparing them to or what exactly they find so unacceptable. Better yet I wonder what type of parts they consider proper (different regions prefer different parts). Are they comparing new sticks to broken in ones, or the parts inside or just think because it feels light that it unusable? I have a feeling most people who complain haven't taken one apart to see what micro switches are even used or even know much about who that company is in the industry.
I guess I'm not going to defend any controller less than $200 as it's usually just a starting point, however blind hatred style complaints over a functional replica stick with some good switches, PC and PS3 compatibility at $50 seem like the opinion of someone who really isn't into arcade sticks.
If you are buying this stick for competitions then you likely wouldn't be happy with this, the PS3 Neo Geo 2, nor the original AES. For competitions, stick to customs or the known brands.