The SanDisk Cruzer 128GB USB 2.0 Flash Drive (SDCZ36-128G-B35) worked for me and has been working for me for the past week or so since I got it. No issues and everything runs fine. I have about 100 ps1 games, 100 mame/neogeo games, and 100 snes games.
I also have this usb hub, Insignia™ - 4-Port USB 2.0 Hub - Black, and am able to play 2-player games with no issue. I connect it to the first usb slot and connect 2 controllers to it. No internal mods on anything.