Both of these can be found on Amazon but they are VERY expensive for some reason.. You can also find them on Ebay, but the best place to find them... If you have one of those shops where you can go trade in old computer games or old computers, or pawn broker stores where you can sell your old items...

Im using a usb audio interface with a midi in port and play with ezdrummers sounds with my electronic drum kit. Doubt it's possible on rock band/guitar hero drums.