AccurateLTD Exhaust sells excellent reproductions. These people have been in the business for a good long while and I purchased my replacement tips for my 1969 340 Swinger from this group. Very satisfied with the product and service.
They are usually at all the big Mopar shows (Chryslers@Carlisle, Mopars at the Strip, I'm not sure about the Nats).
http://www.accurateltd.com/