Just out of curiosity why do you need a 1/2 rather than 3/8 and are you doing so much 1/2 bends that it would be annoying to use the 1” side for it.
One option would be to carefully cut a piece of sheet metal (maybe folded or use tape to thicken it) and jam it in the 1” side so that your metal stops at 1/2 every time. Or put sheet metal screws through the 1” side and cut them flush with a grinder to stop metal at 1/2”...just a thought because idk if you can find 1/2 x 3/8 anywhere.