Is there any 4 player adapter that works for both systems? Sony says no, and while I did find one made by Pelican that bragged it worked all all three (PSX, PS1, PS2) all it managed to do is fry my memory card slot's power on my PSX.
Luckily my PS2 is fine.
I know, buy the Magic MOD and just get a 4plyr for the PS2, but no place near by that I know of will install one. Though, a Sony Service Center is just around the corner, I doubt they'd be helpful.