Finding Gluten Free Beer can be a challenging task. Most places don't even know what Gluten is as I didn't prior to be diagnosed with leaky gut syndrome. I've had the best luck finding some at Whole Foods. However, a couple larger sized liquor stores now carry it in the Indianapolis area. In the Chicago area, Binnys and Kenwood Liquors are usually a sure bet. Kenwood has the best prices out of anywhere.
There are only 3 Gluten Free Beers, that I know of, sold in the U.S. My favorite, or the one I dislike the least, is New Grist made by Lakeland Brewery in Wisconsin. Switching from Miller Genuine Draft Light to Gluten Free Beer was not a very smooth transition. The Gluten Frees are made more-less of Sorghum and Rice and take some getting used to, to say the least. My 2nd favorite is ANHEUSER Busch's Redbridge, followed by Bard's Tale. Honestly, if I can't find the New Grist, I typically will go with Vodka drinks.