"I already need dentures" is one of the best answers to this sort of advice that I've seen, but actually the ramifications could be a broken jaw or even neck, which just isn't worth it. I can't tell what size it is, but the style of that stem may mean that it's 1 1/8", so harder to find a replacement. But I wouldn't use it.

As a last ditch effort you could try running a course thread tap through it and use a matching bolt. The more aggressive course threads are a little larger and might hold but it might vibrate loose periodically and need retightening.

Not necessarily so. For the same major diameter a course thread uses a smaller tap drill diameter. So a stripped fine thread, in a hole, has less material the what the course tap wants. You are correct if the stripped part was a male threaded bolt though. Andy.

I got that.

I was just surprised that AnkleWork connected that post to this one...

Actually, the wing nut is not a bad idea.

The wings would keep it from spinning so it could get tight.

Yes, wing nuts are not as strong as machine nuts but they are still stronger than aluminum.

Just attach that one bolt and then work the cover plate in place over the HB and install the bolt that is not stripped...

These posts make me cringe. This aluminum stem has asked to be retired. The OP should honor that request, spend $10-15 on a used stem and have his eyes open to replace that in the next couple of years with a stem he knows the history of. Aluminum doesn't last forever. Failures are usually sudden, often while JRA. Failure here will almost certainly involve real injury and $$ to the bike (fork and front wheel often do not do well when stems fail). For this stem., the first failure happened while not riding. Good! Now replace it! And enjoy riding with peace of mind.

Ben

It is better to answer the questioner than the question. To do that one must understand the context.