I thought of recommending a log (below), then realized our might be able to lift more than such a contraption could hold (not to mention diameter is a bit large), so now I am thinking using concrete in a 10" sewer pipe with 6" hole drilled for a 6" PVC pipe (to act as holes for the hands and part of the form), and a 2" metal pipe perpendicular to the PVC pipe for handles.
At least one piece of steel on each side of the handle (this would be 4 total) to act as rebar. If you were to have a 6" pipe centered in the middle of the 10" pipe (it would be in 3 notched pieces to fit around the 2 cross-through 6" pipes that serve a hand ‘tunnels’) the contraption would be around 200 lbs. Caulking the joints should hold the concrete in until it sets. You can load the ends of the 6" middle pipe with rocks for extra weight using a plug on each end to hold it in.
Stupid Initial Idea:
For your log, why don’t you get an actual log (15-17" diameter) and bore a couple large holes say around 5-6" and then perpendicular to that, bore some 2" holes for a pipe (that’s right, a thick grip log).
For weights, another 2-3’ length of 2" pipe with a flange welded half way. Bore a 2" hole 1.5-2’ deep, stick the pipe in, lag bolt it through the flange to the log.