There is a very simple answer. But a set of calipers from eBay. If you have a bearing and seal going down, remove the bearing and measure the of, I'd, and thickness of your bearing. Get on the interweb and type in you dimensions. With a little looking you will find the bearing number. The same with the seal. Go to eBay , type in number.
You can save a lot of money this way. Make sure you purchase either Tomlin, SKF, Fafnir, or National, or CR Chicago Rawhide. All quality USA bearings or seals. I normally don't buy from bearings and seals from the manufacturer, most of their parts come from China, much.