TOPIC:

Can anyone recommend a vendor which sells caliper pistons at a halfway reasonable price?
My 1979 KZ 650 SR has a rusted and pitted front brake caliper piston.  
Not sure if the dual front brake caliper on the SR has the same size piston as the single caliper models.

Thanks

I hope this chart helps to find the right piston to your bike. (Höhe = Height)

 

Kawasaki.com and Partzilla have diagrams. Partzilla is easier to use & has a cross-reference.
If the piston & other stuff are NLA, check the part numbers on EB >> NOS might be available.
Alternatively, check the K&L catalog for caliper pistons & rebuild kits. 
Some guys don't like K&L but I've never had a problem. and you may not have a choice if oem isn't available.

ps: I saw 2 piston part numbers at partzilla >> the original may be superseded by a newer part or something. maybe the seals as well. you'll have to figure that out.