general nanosystems, a mile or 2 tops from the space, usually has one for $10, and pretty much always has one for $20.
$10 one: http://nanosys1.com/net-w-oem-wifi-n-150.html
I went to General Nanosystems yesterday and got one of the $10 ones, $10.77 with tax, I think. I asked if they had one that would work good with Linux, and they showed me one at $24. I decided to try the $10 model first. So... I plugged the thing into a machine running Linux Mint and it worked straight away without having to install the driver provided with the stick. This really surprised me, though I had previously installed some of the software packages for wireless, and that may have helped. Using it for several hours yesterday I didn't note any significant troubles with it either.