Yeah, they work great with netstumbler. And yeah, well done on noticing the differences with the Proxim, crap, cards.
As for getting hold of one... I've seen them on ebay.co.uk a few times, they're expensive though. You can get them off expansys.com for stupid amounts of money, far much more than they're worth. The best price is fond on ebay.com, but, you'll have to get it shipped from the US, this shouldn't be a problem, I've done it before.
As for a max USB cable distance, this is something I know little about.
