Spar varnish is always a good choice for something like that. Get a quality one, the more expensive ones hold up to uv better. Helmsman is one I’ve used and like.
I just reconditioned an old boat paddle, 4 coats of minwax helmsman in semi gloss did the trick for me. It’s has a nice sheen to it. You’ll probably need to recoat every year or so depending on usage. I was fixing to go buy a new one but this one is so old, I had to give it new life. I just hate throwing things away that can be repurposed or reused. Lately I’ve been tearing down pallets from work and reusing the wood for all sorts of things.