Home made Moxie

Now that moxie is owned by a coke bottler, I decided to try and make my own.
Prior requests to the many names the holding company used to have (monarch-nugrape/moxie-nugrape/etc.) which seemed to change every other month for some reason led to a single response that the syrup was not for sale. No response from the bottler.

A post in another forum suggested a 50/50 split of root beer and cola, with angastora bitters added to taste. I did this with the "natural sweetened" syrup from soda stream for both (I will be using sprecher's syrup later which is much cheaper and better, I just didn't want to buy half a gallon each). Tasty, but not quite.

Any thoughts? Any suggestions?

All I know about Moxie is that gentian is the main bittering agent. You might want to try a tincture of gentian root in grain alcohol instead of the Angostura bitters (although those contain gentian root, too), but I don't know what other flavorings might be in play.