Mark XI service in NYC?

Hi all - first post here.

I have a few Mark Xs and XI's from my days of being a flea market hound in the
UK 30+ years ago.

They're in pretty good order, but I'd like to get them (or at least one that I
wear sometimes) serviced.

Official IWC here declines to do it as they "don't make the parts anymore"
(although it doesn't need any parts, afaik!)

any suggestions on where to go for a service then?

thanks!

Lookfor reputable and experienced independent watchmakers who specialize in vintage watches or have expertise in servicing IWC timepieces. They may have access to alternative sources for parts or be skilled at repairing and maintaining vintage models.