You could try clear fingernail polish especially on bolts that aren't likely to be undone again for a while.

Stainless tools are aimed at the boatie market. I can guarantee you will pay two, three even five times the price of a normal similar tool.

I have toured extensively in wettish climates. The little crescent wrench I have has done many thousands of miles. It gets rusty occasionally, but not so it's unusable. If getting tools wet is an issue on tour, use a small dry bag to pack them; when I used one, it used to hang from the rails of my saddle behind the seatpost.