I recently bought a single slot Compaq expansion sleeve for my iPaq (802.11b radio card) off
www.mobileplanet.com for about $129 (new). Seemed to be a good price and comparable to those auctioning on eBay. They shipped right away and didn't screw me on the shipping charges.
Link:
http://www.mobileplanet.com/product....97K6&listing=1
Enjoy!