I would remove the sub frame and extracted the broken bolt. If you order a used frame section make sure it is not bent before installing it or you will end up worse off than you are.
I broke the foot peg mount bolt off in mine. I worked for 2 days trying to extract it, to no avail. Buying one from Pinwall was the way to go. I'm sure they can get bent in a wreck, but because of where it's at I suspect most survive even major wrecks just fine.