As far as the best ???, but I use JB Weld because that is what I had. don't use the 5 min quick set as the regular holds better.
I my experience the rusting between the magnet and the flywheel is why they come loose so clean it thoroughly and wipe down with a good solvent like lacquer thinner or acetone etc. Wipe some epoxy on both parts to insure that there is good coverage and then put them together with the proper spacing and wiggle them a little before you use some claps to hold them tight while they cure.
By the way if two have come off the others might not be far behind.
I think that the new epoxies stick better than the original glue that seems to be like a thin sheet between the magnet and flywheel.
