There are no alcoholic beverages made from the "nectar" of flowers per se. It would be very difficult/expensive to collect 100% flower nectar straight from flowers in sufficient quantities to make a beverage. Having said that, [honey][1] is essentially flower nectar collected by bees and regurgitated in the hive as a future food source. You can enjoy fermented Honey as [Mead][2] in a wide variety of flavors and flower varieties. Bees store the nectar in a "honey stomach" so there is no digestion of the nectar. [Read in more detail here:][3]

> "Although many sources refer to the honey bee crop as the 'honey
> stomach,' it is not a place where consumed foods are being digested in
> honey bees."
> 
> In their book, Honey Bee Biology and Beekeeping, authors Dewey Caron
> and Lawrence John "Larry" Connor define the honey stomach as a a
> "honey sac."
> 
> It's "an enlargement of the posterior end of the esophagus in the bee
> abdomen in which the bee carries the nectar from flower to hive."
> 
> Bee vomit? No way. It's where nectar is stored. It's not a stomach as
> we know it.

As mentioned before, beer is made with a flower called hops. There are many other beers and meads flavored with dried flowers. 

As for where to buy Mead, you can most likely find it any decent beer/wine/liquor store and easily by searching the web.


  [1]: https://en.wikipedia.org/wiki/Honey
  [2]: https://en.wikipedia.org/wiki/Mead
  [3]: http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=15512