The bolt broke in half across the threads? The piece inside is the full diameter?
If so can you see it? Tried to fish around with a magnet or tweezers or something ? If you could get it lined back up with the hole maybe you could get it started in the threads?
Tough situation for sure. I don't know if the oil screen hole is big enough to fit the bolt through. The only other hole into the transmission I can think of would be the shift shaft.
Full Diameter. No chance of getting it lined back up I dont think, and then getting pressure and turns on it.