Considering the function of the part only: There is no reason why the wedge can not be made of wood, or plastic. Or you can use a limb from a tree. A nice touch is the stud to fasten the wedge so that it doesn't get lost. It ought to be worth one Euro? I had a wooden rear bumper on a Datsun wagon once: Carved into it was: "Mom's car". It was very functional. Much better than today's painted vinyl bumpers. It hardly showed any bumps.
'69 280SL,Signal Red,113044-12-007537,tired engineer, West-Seattle,WA