Be bold. Go to a store that you frequently shop at or a restaurant where you frequently eat and ask what they'll let you make there. You'll probably do better with a local business than a chain store, and if you're sharing your project, they'll probably appreciate the publicity.
There was only one place in my mind as soon as I read today's assignment! Before work, i walked over to my favorite little neighborhood bakery: Life Of Pie. I often have lunch there, and their scones/cupcakes/cookies are to die for. And since today is Pi(e) Day (3/14), where else could i go? :)
Unfortunately, I wasn't feeling very bold and so didn't mention anything about the assignment while buying a double berry scone (just-out-of-the-oven warm... *drool*). Sitting by the window and making this little cupcake out of scone crumbs and pieces was both fun and delicious.