Shimano MTB Shifter - Stripped Thread Repair?

Hello,

I have an 1992 vintage MTB that uses a Shimano Rapidfire brake
lever/integrated shifter. The threads in the shifter that hold it to
the brake lever have become stripped and no longer hold. The shifter
is Deore DX group. I believe that the shift lever is model ST-M070 or
071 for the front der.

It appears that this was a suspected issue as Shimano appears to have
put some type of heilicoil liner inside of the shifter to strengthen
the bite in the shifter. I believe a piece of this broke when the
original locktite failed to release upon removal of the attaching
bolt. I suspect that this problem may have been a common one with
these shifters.

Repair Options?

1. Find a real metric heilicoil and install it. Do they even make
metric heilicoils this size and where do I find one?

2. Use some form of Locktite thread former. Would it be strong enough?
Suggestions for a specific product?

3. Glue it back together with J-B Weld and hope that it holds and
never has to be removed again.

4. Anyone happen to have one of these in their junk box that they
would be willing to part with for a reasonable price?

5. Are there other compatible shifters that would fit on these levers
or would I have to replace the whole assembly?

Thanks,

Steve