There are several options open to you.
1. Replace the torque converter.
2. Remove the bolt from the converter.
..........a. Use an Ease Out.
..........b. Use a LH threaded drill bit. (Big box hardware store won't have them.)
..........c. Use a Dremel tool with cut-off wheel, cut X in top, try cross-tip bit for ratchet or screwdriver.
..........d. Weld a bar 10-12 inches long at a 90ยบ angle to the bolt threads.
..........e. Cut bolt off, flush with torque inverter and re-tap hole.
The deal with the Ease Out (LH threads) or the LH drill bits (set drill to run counter-clockwise) is that when either encounter more resistance than the broken bolt has created, the bolt will back out. In the case of the LH drill bits, it will even climb up the bit.