I ordered a 1gb CF memory card from here: http://flashmemorystore.com/compactflash.html . It cost me less than $16 shipped. They seem to have all sizes and price ranges. To my understanding, we don't really need a super fast card, those are mostly for hi-res pictures and stuff like that.

BTW, I have a SanDisk card reader and I think I paid about $15 for it a few years ago.