This sounds expensive.....
Yep it sure does Bones.
As Warp has said, this item is attached to the Block then line bored.
Even if you mange to find another Bearing cap, you will still need to at least check the alignment.
Options,
A) If you don't find another cap, "possibly" you could have your broken cap welded by a CERTIFIED welder, look at Aerospace services.
You would then skim the matting surface (Cap to Block) by an amount to be determined, maybe .010" maybe more.
The Cap would then be bolted to the block and the assembly would be line bored, and not by some back street Hero !
Re-assemble Engine.
B) Machine a new cap from a high grade Alloy.
Do the line boring as above.
Sorry my Friend, but those are the only Serious fixes.
I know, I have been through this before in other Engines.
It can be done, but will not be cheap :-(