Tactical Dynamics LLC specializes in radically skeletonized aluminum accessories for the AR-15 and other rifles. Their latest item is a cheek rest meant for use with AR-15 pistols. It weighs just 8 ounces, fits a standard mil-spec receiver extension, and is available in a number of finish options.
It doesn’t look very comfortable against the cheek, but maybe all those cuts will be nicely radiused.
8 ounces send kind of heavy for a mere cheek rest, but might help balance muzzle heavy pistols.
The fact that it extends past the buffer tube is nice if using it as a counterweight. It would also be a nice extension if we could still shoulder things.