If you are designing a method to replace hard to find bearings with a common bearing, don't use a hard to find thrust bearing or the whole operation won't matter. Try and find a common bearing with the proper thrust size that could be removed and be used, most machine shops don't have the man power or time to custom machine one off parts. If the thrust bearing could be made relatively quick using an already made piece, they will be more likely to try it, but if they have to source a piece of 4" diameter brass or bronze, forget it.
