I need a do-it-yourself recrowning. Any ideas?

I once used the round piece from the 10 pc Rotary rasp set from Harbor Freight tools (Item 35453).  I chucked it into a cordless drill and ran it forwards, then backwards on the crown.  I stuffed paper towels in the barrels first, so that metal pieces don't fall into the barrel.  It was kinda rough, but looking at the lands, etc, it was fine.  Shooting it confirmed it.  Only for barrels that are gone, though.  Mine had fuzz (rust) growing inside.  

Good luck.

tk