You may be better off removing the seal and take it to an industrial bearing supply shop. There is usually a number on the seal that they can use to find one that will fit. Also, if you remove the seal and take the part in they can mic the diameter. I recently went through this will the raw water pump on my Yanmar. The pump seals were leaking. I took the pump to the shop and they found the correct replacement seals for about $6. A new pump was in excess of $600.