This is just a guess, since I don't actually know about the liquor you mentioned, but I would think that Grand Wine & Liquor in Astoria would have it, if anybody does. They're right below the 30th Ave. N train stop. It's a great place.
Their number is (718) 728-2520.
re: Steven Stern
They've got it! A million thanks, Steven. FYI, Becherovka is a really tasty, "natural" herb liquer that is thought to have medicinal properties. It's not too sweet, kind of gingery and tangy - not foul and processed like Jagermeister (gack) or something. A Beton (Becherovka and tonic water) tastes like a strong ginger beer, and I've yet to find a better hangover remedy or light cocktail.
They may have it in the city at Astor Place Liquors. They seem to have a good selection. It's funny that you like that stuff. I have been to the town in the Czech Republic where they make it. It's not far from Prague.
I've always prefered Fernet Branca myself when it comes to the herbal drinks. great for hangovers as well. Good Luck!