Spark Arrestors for Mufflers?

Obviously, these bikes gotta be a gas for off-highway. In the nanny-golden-state of California, spark arrestors are required for much of the grass, brush, tree-lined, and otherwise off-highway vehicles.

Don't think these existed in 1968, and I don't think anyone worried about the desert catching on fire.

Anyone have experience with this particular issue? Is there a universal arrestor that could fit?

Guess I have to remain a terror on the hi-way for now

I have used Supertrap disk mufflers. They are legal for OHV. Jim

JRC Engineering sells a desert sled style spark arrestor/muffler. A dealer can order it for you:
https://jrcengineering.com/product/jrc-mcm1/