Cometic will have different thickness viton coated steel base gaskets, available through several of the distributors. I'm quite sure there are options for MLS head gasket thicknesses too, but adding to the base is the way I'd go. One gasket is best but I have to stack two (viton/steel) to get what I need right now.
Cometic has available, but try calling a distributor, Ape or CycleX, you'll likely pay less.