Note: This is not a complete turnkey solution. To get a fully functional item you need additional parts from a hardware store. You're only printing the piece that's hard to source.
The fender and the lamp in the photographs are for demonstration purposes only; they are not included.
For the reference installation you need:
1) Top screws; Bolts 3-4mm longer than the ones that attach the plastic fender to the metallic fender support in the front. In my case the original bolts were 8mm, I replaced them with 12mm bolts.
2) Thin rubber sheet; I used 1mm sheet.
3) Mounting plates; two metal plates with holes; I used 10*57mm plates with pre-drilled holes.
4) Two bolts and associated nuts; these need to fit through the holes on the plates above.
Cut pieces of rubber sheet to go 1) between the printed part and the metallic fender support, 2) between the mounting plate and the metallic fender support, 3) between mounting plate and printed part and 4) between the top screws and the printed part.
On the top you will replace the existing fender mounting bolts with longer ones (parts list 1) and put the printed part between the bolts and the metallic support; the bolts go through the holes in the printed part. On the bottom you sandwich the fender support and the printed part between two metallic mounting plates (parts list 3) and tighten it with bolts and nuts (parts list 4).