If you have a movie liquidator in your town then that is a good place to start looking. Next choice is going to be on Ebay.com. Copies pop up for auction on there all the time.
In fact, here is one:
http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=1441132229DISCLAIMER: I have nothing to do with this auction. Buyer beware.
Andrew