What size o-ring does the pacific hydrostar shallow well pump model #47906 take?

I need to know what size o-ring the pacific hydrostar shallow well pump, 1HP, Model 47906 takes. I think the one I now have in it is not the correct one.

This is the nearest manual I could find, but it is not for a 47906. However, you can email [email protected]
And get help there.

http://manuals.harborfreight.com/manuals/69000-69999/69302.pdf