In the past I had very good luck cutting 1/2” rubber conveyor belt using a hand held jigsaw with a knife blade in it rather than a toothed blade.
I first tried a fine tooth blade but it was no fun. Knife blade cut very easily. You could probably make your own by grinding the rear edge of an old blade to a knife edge for a test. It’s been a few years and I don’t remember where I bought the blade. I think Home Depot.
Or even grinding the teeth off a fine tooth blade…
Too much to do...Not enough time...life is too short!