DDR pad for pc

[likvvidx]

since i dont have a pad or a ps at all and i wanna play stepmania on my pc, what should i get? should i get a ddr pad for the comp (usb or serial) or should i get a psx -> pc adapter (usb). I find that it is really hard to find a pad for pc but there are pads for psx everywhere along w/ adapters. the only prob w/ this is that i would have to pay much more for both the pad and adapter than gettin the pc pad alone. If anyoen could help me out.. i would much appreciate it. thx