Def' get one of the new ones the dude at the NEO GEO forums is making. They are GREAT. I tried screwing around with the old ones and could never get them to work. The batteries in them die, I tried replacing, never worked.
I saw a bunch of them on ebay I thought about buying, I also saw the guy doing the march of dimes race had a nos donated to him. I would have liked to get that.