Carbide-Tipped Drill Bit
I haven't had to drill stainless steel myself, but understand that a carbide-tipped drill bit is better than the typical high speed steel bits and would likely work. I believe a lot more expensive solid carbide drill bit is better and is less likely to "walk" when trying to drill.
As I recall, the hole into which the pin screws does not go all the way through. So if you are drilling from the pin side and not the threaded side, won't the drill bit will be trying to tighten it even more? The other options takes little work - buy another brass unit for that side's B pillar.
Good Luck!