This is what Maserati use to cover the locking nuts on a GTS. Unusually, all 5 of the nuts of a GTS locking set lock, not just one per wheel, so the set contains 20 nuts & plastic cap covers with removal tool.
I have to say though they are not great. My car is garaged and yet they have all discoloured a bit and go quite brittle so when I took the front wheels off last month to change the tyres, two of them cracked so they're not the best solution. Maybe these in the link are better made?