If it were me, I'd bore the existing hole out oversize, probably something like 7/16" fine, or even 1/2" fine. Turn a slug of aluminum to the appropriate thread, slather it with JB Weld (or Loctite sleeve retainer or even just red Loctite- whatever suits) and screw 'er in there.
Once it's cured, face it flush, then redrill and tap back to 1/8" pipe. You'll need to make sure the new slug goes in as deep as the crack, and you might have to redrill an internal passage depending on how the air is routed inside the frame (it's been years since I dealt with an AutoTrracer) but it should give you a nice, permanent solution.
For that matter, with a little work, you could even install a vertical ASA- with the sleeved hole, you could reduce it down to a 1/4"-28 bolt hole and attach a 'Cocker ASA.