I got mine from Bunnings, it had a metal bracket. It is a dry powder one, I think that is the only type you can get in a small (1kg) size.
I kno of a guy that had to use one on his interior in a RX7 it put out the fire and saved the car but the powder is corrosive and now his car is rusting to shit, so if you have to use one best you clean it up real good after it is all over.