I got replacements from bunnings, m6 x 25 high tensile hex bolts.
Then I just used a washer on either side if the rubber grommets so it didn't pinch through. Looks pretty good on all up cost me about 10bux.
And Munky is right, don't tighten the shit out of them just do them up enough to squash the rubber a little and then redo after a few heat cycles.
Edit: also don't forget to run a little bit of gasket goo around the back of the cover where the half moons are, they have a tendency to sometimes leak.