I've also bought one time ago for about 18€. Works really good, allows 2 pads being plugged at the same time and without drivers. Drivers are needed for shock/rumble only. Dunno if every adaptor works like it, but I'm very satisfied with this one.
If someone it's interested, it's labeled "Super Dual Box"
Btw, I didn't use so much it 'cause my PSX to PC DPP interface