Protractor, straight-edge, circular saw
Should be able to cut any angle(s) you need, up to 90*.
Can you put a small block/wedge against the fence to hold the material at the desired partial degree? I've used double-sided tape to hold a small block to the fence at a pre-determined distance from the blade, placed the material against the block and the fence near the blade, then made the cut. It'll take some experimenting the get the exact size of the block/wedge, distance from the blade and how much material can extend past the blade.
Cut to plan
File to fit
Paint to hide