Got any authentic Greek restaurants nearby? Also search for "Chios" - this one has a few weeks lead time, not months, on Amazon: https://www.amazon.com/Chios-Mastiha-Natural-Mastic-Growers/dp/B00YSO7KRA

Mahlepi is probably easier to find. I got mine from Amazon and vacuum pack + froze it to save it for whoever cleans out my freezer when I die.

Good luck. Take pictures, put them on Reddit.

Also, you're required to constantly say "fla OOO nass" while making that recipe. fla OOO nass.