Ted, would something like this work for you.I'm using a wrench made by an old AMU Armorer out of a NM op rod. What I'd like to see is a wrench with a head like this one made as a 3/8" drive socket. That way it could be used with a torque wrench.
I just made it for the solid plug I have on one of my Garands. It could easily be made with the cruciform head. In fact I may go whip one out while the mill is still warm... The back has a 3/8" hex and is made from chromoly and parkerized.