Here are the vendors of seals and wax that I patronize.
Kings Wax : Canadian maker of an excellent line of both traditional and glue gun "real" sealing wax (not the plastic-y stuff used for scrapbooking) and Bank of England wax
Letter Seals : stocks a wide array of seal lines and various waxes, including J. Herbin and Waterston's
Nostalgic Impressions : stocks a wide array of seal lines and waxes - the first company from which I EVER ordered wax and/or seals
Seasons-Creations : stocks a wide array of seal lines and waxes, some of which I don't commonly find at other similar sites
Wax Insignias : sellers of mixed metal and sterling silver seal jewelry (charms, fobs, rings) of which some are usable wax seals and others are impressions of seals
There are several talented Etsy vendors who make and retail seals and seal jewelry. It's quite likely that there are wax makers, there, too, but I have not sought any on Etsy.