/me puts away sledgehammer
How good do you want it? Angular contact bearings are what I would recommend, but depending on the design of your spindle, you may have to modify something so that you can preload them against each other. In certain sizes, you can also purchase a double row angular contact that is fairly wide, but takes care of the preloading problem since it is all internal to the bearing. List your bore and housing sizes, and the length of the existing bearing bore available, and I'll look up and see what bearing number you could adapt to it.
Metric dimension bearings are easier to come by. Your spindle may already be .6299 = 16mm, but to those not expecting it, it may appear to be 5/8" until you mic it.