I have tested compatibility on several controllers and I have put together a list of known working controllers.
- Genuine Sony Dual Analog Controller (SCPH-1180)
- Genuine Sony Dual Shock Controller (SCPH-1200)
- Genuine Sony PSone Dual Shock Controller (SCPH-110)
- Genuine Sony Dual Shock 2 Controller (SCPH-10010)
- Official SNK NeoGeo Pad 2 for PlayStation 2
- Namco Arcade Stick for PlayStation
- Hydra Performance Wireless PS2 controller
- MC Cthulhu (with Playstation Cable)
There are probably many more controllers that are compatible, but this is what I currently have on hand to test.