[john hall]

Belzona is some really good stuff--it ain't JB Weld, that's for sure. However, you get what you pay for and you will pay dearly for it. We had to use it on a project at work some years back where we actually had to mill it afterwards. It worked pretty good.
The Loctite looks promising but by the time you order the 3 different things you need, it's going to be pricey also.

Any machine shop should be able to cut you a new key in 30 minutes unless its a woodruff---still doesn't take very long but he may not have the correct cutter. Do yourself a favor and see if you can just get a new key cut on the shaft for a reasonable price. It will be better than a patched keyway. Those repair products are generally used to buy time until the machine can be taken out of service for a long time to replace the shaft. Likewise most industrial stuff is custom (unless we are talking about electric motors or gearboxes) and the shaft would have to be made.