Thanks for all the great information and advice.
I have also consulted with a couple of sources that advise that a parts replacement is not a viable option. Apparently there are two versions of balance wheels for this movement caliber, one that runs at 18K and another that is 19.8K. It's not possible to tell from looking at a balance what speed it runs, and no one selling these balances knows for sure the actual speed.
So the odds of getting the right one that will actually fit my movement and run at the proper speed are slim.