I think i broke rear main bearing

Welding the cap would actually be the way to fix a hard to find part. But if you don't have a welder and those caps are everywhere. I would send some young guys to a motor pile and grab a couple rear mains for $10 . Bring them home and torque them up with your bearing and plastic gauge. Most of them are real close from what I have seen. Luck may be on your side.