I have seen a lot of sites that make/sell controller interfaces for playstation/xbox/wii that actually would let you use any edrum set for rockband. http://edrums.info/control.htm
has links to buy them and also show you how to modify the controller yourself to accept 1/4" inputs from drum pads. this would prob work well if the pads are broken bc even if you messed it up who cares bc its already broken. :)
get the j5 interface box then pickup some cheap drum pads.
please note: i've never done this myself nor have I played rockband besides 1 time in the store so I have no idea what pads work best with it.