http://www.pegasusautoracing.com/
http://www.ogracing.com
try them - on my old Porsche I had something very much like this:
http://www.pegasusautoracing.com/productdetails.asp?RecId=3156
bottle mounted in the rear tire well area, pull line routed back there w/ a handle up front, lines to put out the interior near fueling, and 2 in the engine area. yes, halon can be toxic – iirc it sucks out the O2 in the air – but you get out of the car if you have to pull it…