1201T321 MIL-Spec Viton(R) Fluoroelastomer O-Ring, AS568A Dash Number 932, Packs of 10
From mcmaster online
It's $14 for 10. This is the upper one. I doubt you'll have to change the lower one. I've never had to.
My spare pump isn't available at this time or i would have sent it to you.
The race is long and, in the end, it's only with yourself...