Krylon UV resistant Clear. It's purpose is to keep artwork from fading, and that aside, it's the finish I use for everything. I used to do some testing on the dash of my truck, years ago. Some people were using sunscreen on their exotic wood pieces, and I can tell you from testing that it does not work.I have NOT tested the Krylon UV, but my sense is that it does help to at least some degree. You can't keep the boxelder from changing, though. I have pieces I've had for years that largely stay in a cabinet, but a few days of strong daylight will fade it right away. Some people use acrylic ink to color in the red areas.
Whatever you do, if you sell work, the buyer should know that it will not remain the way it is when they buy it.
John