The most durable paint will always be a catalyzed automotive or industrial coating.
Also prep is at least as important as the paint. The best paint won’t hold up if the surface isn’t properly preped.
Since you asked about spray cans, many paint suppliers can custom mix paint in spray cans, we did this for some repairs on a friends winter beater bmw and it came out ok as far as colour match.
My ‘77 has no factory painted silver pieces but I did paint a plastic propane tank cover with Krylon Fusion and it came out really nice. 3 years outside and it still looks as good as the day I did it.