I've seen these on sale on a few web sites and through Amazon:
Transcend 2GB Micro SD Card w. Memory Stick Pro Duo Adapter (unable to post url)
Apparently they let you use MicroSD cards on the PSP. Has anyone bought one? Do they work well? Do they support MagicGate etc?
It would be awesome if they did, SD cards are about half the price of Sony/Sandisk Memory Sticks