JP offers their 0.936" block made of stainless steel and it has a rail on top.
If you are worried about it moving, just install it real tight, then remove it.
You end up with little circles on the barrel from the set screws.
Center punch the circles and then drill each one about 1/32" deep with a 5/32" drill bit.
When you put the gas block back on, the set screws will end up in the divots you just drilled.
The gas block will not move after that unless the screws actually loosen up.
Red loctite cures all...