I'm smiling here.
Best Buy also put me into fits. Walked in and immediately wanted to walk out. Then I told myself I had to do this. Walked over half the store and bought a DVD I didn't really need. Over the next few weeks I was able to explore the whole store.
For me it was the fact that Best Buy doesn't have carts. Carts=Crutch
Agoraphobia is horrible, but it can be beat by doing the same thing over and over and over again until it becomes boring and reverts to being natural again. The process will wear you out with getting tired from repeated anxiety attacks but it does work. It really does.