hmm i got mine off ebay for about 250AUS... that was about 2008 though... sooo heres a link of one you could get...
http://cgi.ebay.com/ebaymotors/JWT-POP-CHA...sQ5fAccessories
its $65.00 US shipping... its like 1aus = 0.91US sooo its a good buy!
works well! didnt notice much of a power difference however the sound is awesome!!! a massive ROAR!!! xD