Why not just get two longish pieces of steel (~30x1x0.3 cm) & bolt them together into a pivoted X shape but with a longer handle side ie similar to how scissors are pivoted? The business end to taper to a point so it can always engage the cap's lugs. Lumps of angle iron would also work if you ground them down a bit. The angle would help provide structural stiffness.
Then it will adjust to fit just about anything.