I just bought a SuperJoyIII for £6.99 (+ £2.95 postage) on ebay, the seller has 988 left. It's turned up three days later so obviously a reasonably good seller.
Buy at your own risk obviously! but it seems as good a source of NOAC's as any!
on closer inspection, mine appears to have some light corrosion (probably from being stored in a damp warehouse). I haven't tested mine yet, but will this afternoon and confirm whether or not it's worth buying from that ebay auction.
I got mine the other day, only took 1 day to ship, pretty impressed. Took it apart, looks like a standard Super Joy III board, it's pretty small, and seems to follow G-Force's pinouts, I haven't had much time to test yet.