There are two important parts of this particular hole. First and foremost is the seat, which is an angled surface at the bottom of the hole. The bleeder screw bottoms out against this to seal the hole when you tighten it. The second important part of the hole is the threads - they allow the bleeder screw to apply pressure against the seat.
Having said that, the seat is more important than the threads. If the threads are not that bad off, in other words if you can't wiggle a new bleeder once installed, it should seal up reasonably well. It all depends on how much thread is missing.
Regarding the bleeder repair thingy I linked above, I've never used one but it looks to me like you just drill your bleeder hole oversize, tap, and thread in the thingy in the picture. The larger piece goes into your caliper and has it's own bleeder screw and seat. Looks to me like it would do the job and may be cheaper than a new caliper. Also if as RxmanGriff says the Speedbleeder company offers installation service, you could try contacting them and seeing if they can put in a new seat AND a speedbleeder at the same time.
Best of luck
mystic_1