The JB3 is no longer being manufactured. However, you can buy them directly from Creative on ebay for a nice price usually. You use the JB3 because it allows you to record in .wav format which is something that no other models allow. You should spend around $150 us for a new JB3 on ebay, not bad. If you can't find one then you do have 2 other options:
Edirol R1
Edirol R4
There's a few people around here who do use those and like them alot. They allow 24bit recording and the JB3 only allows 16bit, so they will sound better. The a/d converter is also better. The drawback is the price...look for yourself.
If you can't find a JB3 and can't afford an Edirol, you do have options. You could use a Minidisc, Hi-MD, DAT, Laptop. If you are open taping (not stealth) and have a laptop already, install a good sound card and use that instead of buying something else. Minidisc only get 80 minutes per disc, then you have to switch. Hi-MD gets 90 minutes per disc. DAT gets up to 3 hours per tape, but has a hefty price tag new. Don't forget than you need mics and other stuff too, so don't skimp on those in trade for an expensive recorder, spend as much as you can on your mics and whatever else is between your mics and recorder, you'll be very very glad you did later!