I have a craftsman riding mower with a Briggs & Stratton v-twin engine.  Engine model 40H777-0241E1.  Everywhere I look I find part number 698430 for the piston rings.    That part number is not available for purchase anywhere.  Is there a replacement set of rings that I can buy for this engine?  Are there other part numbers that should fit these pistons?  I am at a loss and would love to get my mower back up and running again.
 
Thanks!