FWIW, I bought a 4GB miniSD from www.flashmemorystore.com and it's working great. Preferred to go this route over the eBay auction in case it didn't work so that I could get my money back.

Had a 4GB microdrive and a 2GB SD in my Axim X50V, so it's nice to have some real storage capacity again! Looking forward to the 8 and 16GB versions someday...