Pull the bearing and look on the race for the numbers. Give these numbers to your bearing retailer and tell them you want a SKF bearing to match. If the numbers are not legable measure the OD x ID and thickness and give theses numbers to you bearing retailer.
Numbers will be something like 6206RS (60mm x 30mm x 16mm). 6206 is common within most bearing manufacturers as the "RS", It stands for "rubber seal"
While your swing arm is out also get the pivot bearing sizes and seal sizes. I can get you the 3 bearings and 2 seals for about $40 USD. Don t know what shipping would be though. Bearings are KOYO.