Some times you just need a little more pressure 🙂
Screw type nipple clamps with a hole in the tail allowing for the addition of some rope or chain.
I found that printing the screw and nut at a reslotion of 0.1 at with 6 solid layers and an infill of 25% worked well.
Then printing the body at 0.2 with 6 solid layers and an infill of 20% did the job nicely.
Best material seemed to be ABS with acetone polishing.
The reason the original design had the thread inserted in to the bottom however if you crank down on the screw and strip the thread having a seperate insert makes it easier to repair/replace.
Approx 68mm long, 15mm thick, 38mm high excluding the nut.