I think i broke rear main bearing

Really the only proper way would be to find another block. You could look for a rear main cap from a scrap block. That requires engine removal and complete disassembly to enable align honing the mains for proper alignment of the new main cap.
Taking the cap to a machine or welding shop to be spray welded while bolted to another block is an option.
A welding shop could weld it clamping the broken piece into place and grinding the crack to use a nickel rod or braze it. Then install a helicoil or Keensert. Not much metal to support the Keensert, so I would helicoil it. Being the oil pump mount bolt holes they do not require tightening the crap out of them. I would be inclined to braze it with the helicoil. Just grind the crack down to the threads before welding. Cast iron rod is another possibility but involves preheating and tapping with a chipping hammer while allowing to cool slowly to stress relieve. A good welder should know the proper procedure. My concern with cast iron rod is warping, requiring the align hone.