For stainles steel on aluminium use MONEL rivets.
To avoid corrosion put TEF-GEL (or DURALAC) on the rivets.
According to some people, TEF-GEL is better than DURALAC: "We are a mast (alu) and boom (alu, carbon, glass) builder. We strongly recomment Tefgel. It is far more better than Duralac that we used in the past. Even after many years there is no corrosion around the bolt and you unscrew them easily. It prevents electrolise as well. Best regards. Peter Zelhorst."