Hey Joel,
You might try GS Gunsmith in Maple Grove. I have not used them, however.
I had a similar issue with my Browning A5; the fix, screw a very small screw into the threaded hole and paint it white. It works! If the whole mounted assy. broke off, that's another problem...
Check with Brownell's or Midwest Gun - they may have a replacement sight. Good Luck.