Stainless is a bad conductor but if the bolt is only clamping and not serving any conductor role on your post (stud for example) you’re fine. Stainless will prob eventually get nasty but take longer.
I still vote brass, I mean you’re going to look for hardware you can buy brass hardware usually at the same store as stainless in plumbing I’d do the whole post but that’s me. If you do have an electrolyte leaking out slowly like possible, those pads are a good idea if anything just to slow or baffle whatever comes out. I’d perfectly clean the post, attach on a perfectly cleaned terminal, and get some spray coating to trap the connection so it has just another barrier to work through.
If you have an exploded battery laying around like I do you could neutralize the plastic on a portion, use gloves and take a piece of the shell, cut an opening the size of the post and make yourself an acid resistant skirt for the top. Would limit the amount of area to use, but it could be made thin.