While trying to loosen the bolt on this stem I have rounded/stripped the bolt head somewhat. Yes, I was using the correct size allen wrench!
The left side bolt did come out, and appears to have some lock-tite on it, so I'm guessing the right side does also. It's really stuck in there.



So 2 questions
1. is there a good way to get this bolt out?

2. where can I get a replacement bolt?

Thanks!

I can only think of one way to try.
Use a hacksaw to cut accross the head, making a flat head screwdriver slot.
Use a sodering gun and heat the bolt with it, this will loosen the lock-tite.
Then use a flathead screwdriver or chisel and tap the slot to lossen the bolt.

I have done this hacksaw slot on bolts I've snaped the head off of ! An it works most of the time.

As for getting a new bolt, your local LBS should have one.

These stems vary quite a bit in the details of the design. Many have one side keyed or splined and not able to turn. Others loosen from either side.

It's also possible that there's lock-tite on one or both sides, then there my be corrosion. All in all, it's possible that there's no non-destructive way to take this one apart now. Even if you could get it apart, there's no assurance that replacement parts are available.

So you have 2 choices, either remove and replace the stem or decide you can live with it the way it is.

BTW- I hope you only wanted to change the angle. If you want to remove the stem, the bolt you need is under the plastic cover in the center.

You may be able to use a strong epoxy to fasten a sacrificial hex driver into the mangled drive recess, or pound an oversized or Torx driver into the recess. Or, since stems are cheap and easily available, just replace the stem.

Hammer a cheap torx bit in there,that should take it out.As was said, make sure your taking out the correct side,some only remove from one side.

I've removed similar with a soldering iron, a dremel, and a flathead screwdriver, I slotted the bolt with the dremel so it fit a larger flathead screwdriver snugly, then heated the bolt with the soldering iron for a very short perioud, inserted the screwdriver head and it unscrewed easily... dunno if that helps any but hey it might.

Too late to help now but for future reference, allen keys are not long tem investments and do wear out and loose their sharp corners with use. So, despite using the correct size, if it was worn what you experienced is easy to understand. Even good quality allen keys are cheap so replace them often or cut off the worn end (a Dremmel with a cut-off wheel works well) periodically to refresh the shape.

+1 on new hex keys. BTW, cheap ones made from Chinese monkey metal and the ball end type will strip fasteners more easily than a new, close-fitting one made of good steel.