I friend of mine created a custom mount for the GMRS-Pro radio. The mount holds the radio’s belt clip and should provide a good fit. I’ve ridden hundreds of miles with no issues.
My friend used the 3d print file and printed 2 for me. He was concerned with the 20% fill being too weak, so he bumped it up to 35% fill. The holster is still ultra-lightweight. I attached a RAM ball mount, and it looks great. I expect to take a ride soon, but it looks and feels like a solid radio holster.