Having just repaired a couple of Mercer dial test indicators I have some 1/32nd inch dia bearing balls available. 8p each plus postage. (5 balls each side of the stylus pivot). I also have 900 odd 1.5mm balls if anyone needs any. (Repaired a linear slide). 50p for 10 including postage.
This is not a commercial plug, just seems silly to have them on the shelf forever.