The dimensions are not critical,any three or four lb. weight will do.
Mine is a wrist pin out of diesel truck engine. Available at the dumpster at your local truck garage.
However dimensions are as follows, all the legs are 7" long with an additional 1 l/2" turned down 90 degrees
and sharpened to a point.I used 3/8" round stock.Back legs spread apart about 60 degrees.
My wrist pin is 4 1/2" long & 2" in diameter, it weighs 4 1/2 lbs.