There is SDHC cards in the same store I bought my GP2X-Wiz ( http://www.adictron.eu ) and they have even better price than what I read in this thread:
2GB SanDisk - 4,95€
4GB SanDisk - 7,95€
8GB SanDisk - 12,95€
Adictron overall have very good price in all stuff. And yes, they ship to Europe with cash payment on delivery available.