I'm replacing the turn signal lenses on my 1989 244. The old ones had rust stains around the screws - I assumed the screws were rusty, but when I got them off it turned out to be the fasteners underneath that had rusted out under the chrome plating (little metal nuts pressed onto the plastic bosses in the turn signal bucket).

I'd hate to put brand new lenses on these fasteners and have them look awful in just a few months. Is there any way to replace these without buying all-new turn signals? Are the little press-on nuts available anywhere?

Thanks in advance...