Roller end caps from pvc or nylon Help!

[Jonathan]

It would be best to have the bearings to hand as well, they may say 30mm outside race but I bet their not spot on and would read different on two different callipers.

Bearings will never differ enough to measure with a caliper. I'm pretty sure the tolerance for that size is something in the tenths of micrometers region, so even with a micrometer you'd struggle.
Being able to change the bearing is a point, but iff the bearing is broken anyway there's surely nothing wrong with applying a large force to the inner ring to remove it.