There are several suppliers out there that have spray products for various OEM leather and vinyl interior colors. One highly rated supplier is Colorbond. You can check their website and find the Dark Slate Gray & Medium Slate Gray colors, along with other colors Chrysler used. Colorbond can be found on Amazon also.
Here's a link to another supplier (SEM) available on Amazon:
CLICK You may not need to apply an Adhesion Promoter as a prep coat since many of these products are advertised as 'flexible coatings'. But you most likely will need to clean the surface thoroughly to remove any treatments (i.e., leather conditioner, Amorall, etc.). that may have been applied over the years. Surface will need to be 'oil-free' so to speak.
If you only need to do some spot touchups, the supplier on eBay (that I sent you links for) is probably your best option.
Good Luck to you.