I've looked into this myself. As far as I could tell, You'd have to have access to a milling machine and some weaver base stock in order to make one yourself. Wouldn't be too difficult, but it'd involve some serious gunsmithing. I didn't find any bases that would fit the barrel. The closest thing I found was the Springfield Armory Scout Scope mount for their M-1A. The major problem with this barrel clamp mount is the clearance of the operating rod. Also, a look at the barrel in the area just forward of the receiver shows an unusual stepped taper style. My opinion? I'd stick with Iron Sights and buy a Bolt Action to mount a scope to.
What I found was that the barrel diameteron the Garand was about the same as a Ruger MKII Pistol Mount. If you can find a high mount for the Ruger, you might be able to adapt it to the Garand. Check Brownells and your local gunsmith.
