Hiya bud,
I've brought 3 8gb sony memork pro duos from ebay. I doubt they are genuine sonys as they were 23.49p delivered each but they are spot on.
The guy is very reliable and the card arrives within 2 days each time. The downside is the transfer rate when putting games or anything on it is about 50% slower, with 3mb/s being about the peak.
But any game wouldnt take more than 5-6 mins even the largest 1.5gb ones, simply compress them into cso before hand and save yourself some time.