Thanks for the imput everyone. I’ll probably run it over to Home Depot and get an extractor. I wouldn’t mind buying a new one if I got some use out of the one I paid $50 for, but these things should last longer than that.
That mount is potentially in an area that will see a lot of sweat and sports drink, which can lead to corrosion. If the threads weren’t greased, it may make a difference next time.
A stripped bolt on a piece like this is more of an “oops” moment and not a product failure.
If you can’t get the easy-out / bolt extractor to work, just get a drill bit that would fit inside the hole in the aluminum arm. Drill the head completely off, but do not drill into the threaded mount piece. The arm should fall off once the head is gone, leaving the remaining portion of bolt like a “post” in the threaded mount. Clamp on some vise grips and you’ll have it out in no time.