Yes, of course, you can buy the gasket from the Mazda dealer. I think that's the only place you can usually get it. The last time I tried to get one from a local parts store they said they didn't have it. (But a new gasket does come with a new tank, if you purchase one. )
I don't know the part number offhand but the dealer should be able to look it up for you. You can also get the screws for the fuel pump for cheap.
A forum community dedicated to Mazda MX-6 owners and enthusiasts. Come join the discussion about restorations, performance, upgrades, modifications, classifieds, troubleshooting, maintenance, and more!