The best source for that beer you crave is your local beer store. I know you've already looked there but if you didn't ask the clerk or owner if they can order your beer for you then you've only scratched the surface. Beer stores are limited to only carrying a few of the beers available to them by their physical shelf space. In almost all cases, there are many more beers available in a given distribution area than appear on the store shelves.
Here in the US, most beer distribution is the same in any given area. This means that if you asked about your beer at one store, the next store down the street will have the same selection available for special order. Distribution changes drastically across state lines. If you live near a neighboring state, the beer stores there will have access to beers not locally available and vice-versa. Be sure to check in both states for that special beer you've been seeking.
Be prepared to order a whole case. Beer stores won't usually order a beer that they don't regularly stock unless they know that they can sell the whole case. Besides, you probably wouldn't mind having four 6-packs of your beloved beer, would you?