there are quite a few on ebay...one there at the moment in fact:
http://cgi.ebay.com.au/NASCO-WARMARIDE-HEATER_W0QQitemZ190002920876QQihZ009QQcategoryZ32058QQrdZ1QQcmdZViewItemyou will probably have to pay in the region of $200 for a good one. If you do a search on 'warmaride heater' on this forum you will find lots of info. Pretty easy to fit if you don't mind drilling holes in your firewall (
). Also if you are running a red motor you may need to find a Bosch heater core to withstand the increased coolant pressure...once again lots of info on this will be pulled up with a search....
Jonno