Bearings on Tow Dolly. Where to get? Any tips?

Any NAPA or bearing store will have them. In the yellow pages look under Bearings, or automotive / equipment parts and then bearings.

You should take the P/Ns with you or call them first. Or you need the mfg and capacity of the axles. They need something to go by, but the're readily available. Then get a pint of axle grease.

Bill