Suggestions for keeping brakes clean on road trip

Last summer, while on a long road trip with my bike on a rear rack, my disc brakes ended up contaminated from the grime of the road.

I’ve looked for a product to cover the brakes (and maybe drive train?), but the best I’ve found are covers for doing maintenance, such as these from Muc Off:

https://us.muc-off.com/products/disc-brake-covers-with-free-m094

Has anyone tried using these as a cover to protect brakes from getting dirty when driving at highway speeds? Do they secure well enough to stay on the wheels for long periods of high-speed driving?

Or does anyone have any alternative suggestions for how to keep the brakes free from contaminants?