Not sure on where you could get them in the US but the ones we tend to us are SKF Y Bearings with grub screws, 35mm ID, 72mm OD. They are all a standard size of 19mm to fit in the bearing carriers.
They only options is that you can have a choice of speed and load rating. By guessing I presume we use the highest with part number of YAR-207-2RF
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