Its easy peasy, if you have the cocoa. Go to a restuarant supply house, and get a big ole back of dutch cocoa, then gather up the following:

1 1/2 cups water
3 cups sugar
1 1/2 cups Dutch-processed cocoa
1 tablespoon vanilla extract
1/4 teaspoon kosher salt

bring the water to boil with the sugar, slowly blend in the cocoa, salt and vanilla extract. Whisk it till it's smooth, and then reduce until it's thick, stirring often (but not non-stop). Let it cool, but keep the whisk handy for scaring away the inevitable children hoping to sneak their fingers into the now-cooling concoction.

Pour into a squeeze bottle, and you ahve syrup that is better than the stuff in the can!