If the shackle is of quality material, a sleeve cut from roll bar tubing off the floor, will give you a suitably large radius.
It does not have to fit the cross pin tightly, and can be done for cheap.
The length must fit to 0 gap so the material won't be pinched at the end of the sleeve, and that is true for any assembly.
Paint it silver and just tell them it is stainless.
