Your best bet is to just eBay search for one...that's how I got mine, and they can run anywhere from $45 to $100 if possible, get a warranty. A good seller will offer one for a working motor. Also, good detailed pictures are helpful. Now the tricky part is the installation. The motor has a built in spyro gear that acts as a timer so that it knows when to stop at the end of the track and in the flip up mode. The best way to get it in sync is to plug it in prior to installing it (aka, have it hanging from the wires and have the switch plugged in). Run it back and forward (open and close) and you can figure out when it is in the closed position between the long spin (closing) and the short spin (flip up). If you have your roof in the closed position, make sure you have the motor in the closed position (between the short and long spin of the motor).
Well, hope this helps. Here's an old eBay listing to give you an idea:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33706&item=7965532910&rd=1&ssPageName=WDVW 
