To find hub replacement bearings, start by looking at the old hub bearings. Use the numbers printed on the seal to source your replacement. Find another bearing with the same numbers. Just make note of what type of bearing it is.
When measuring for new bearings, there are 3 dimensions you need: axel diameter (where the bearing rests on the axel), hub bore diameter (where the bearing sits in the hub), and the hub’s bore depth.
Start by measuring entire depth of hub bore, then measure width of any seal or end caps that sit into the hub bore. The width of the bearing is the difference between those two measurements.