For what year or body style? Some years the brackets are welded on the firewall. I've had good luck in the past finding them in the various central California salvage yards. where are you located? There are lots of yards around Sacramento / Rancho Cordova area that will pull parts and ship. It isn't a total unicorn, you just have to go somewhere with lots of work trucks. In my experience, the hydraulic clutch bell housing, especially without cracks, is much harder to find.
Good luck!