Like Eddie said Partzilla may have exactly what you need. CMS. is also a good place to look.
https://www.cmsnl.com/suzuki-gz250-m...l#.YO9UnuhKi9g. If you don't like their prices, (shipping can add up fast) you can copy the product number listed for whatever you're looking for and paste it into ebay search box along with a short description, in this case (bearing).
Chances are pretty good you'll find what you're looking for and possibly save yourself a few bucks too. I just finished restoring a 47 year old Yamaha which needed lots of new parts and I was able to find most of them just that way.