Magician said:
Are you suggesting something like this Mushiki?
If I remember correctly that one used to cost quite a bit more.
I bought a ps cyphergames pad and it's alright, though I had to mod the arrows. One of the contacts broke but not by itself, my friend broke it... so I don't know how well it'll work with the PS to X-box and GC converter.

I was all ready to play Ultramix too. And I'm too busy to try to fix it.
But yeah if you're serious, metal pads are the way to go, either to get those cobalt fluxes or whatever, or a cheap one that you can mod yourself.
If you are just a casual player though and want one that's decent, try to track down an official konami one. They were released a couple weeks after the bundle was, but before the game on it's own was. I don't have a link, but I've seen them at both Gamestop and EB, so call and ask for the official ones.