Look for a shooting stick, which is basically a simple, generally telescoping aluminum monopod for a rifle. Usually has a rubberized wide v groove to set the rifle's forend in while shooting. The groove is often fairly wide to accommodate certain rifles and should handle even a big aluminum top tube. Some double as a monopod for a camera, so the v part is attached with a 1/4x20 screw. Might even get lucky and find one just the right length to use as is. I've also seen the shooting top offered with a telescoping hiking pole, which had the secondary benefit of a textured carbide tip that can make its own divot in ice or rock to stay put.