you would have to specify if digital pads are fine for you or not. there are ps2 titles notorious for not working with digital pads. you also would not be able to acheive true analog function, and even simulated analog would be tough to come by. i am unsure of whether the dc adapter supports analog or not.
that said, i have 4 digital psx pads and a 4 player parallel port adapter i may be willing to sell. i could also wire the pads if needed. that way, you could still have a pc in there. otherwise, you may try getting an x-arcade controller. they have adapters that are guaranteed to work with ps2, dc, etc.