One of my mechanic friends gave me this little tip. I purchased some "bellows gasket cement" I think it is made by Mercury Quicksilver, I use a few dabs of it on the top rim of the canister and then center the gasket on top of the canister than apply a few dabs of cement to the top of the gasket and than bolt it into place. I let it set up and dry and then fill the canister from the top with fresh diesel fuel once everything is back together.
Hope that helps