Use something easy to start with. Grab a barbeque with wheels on it and walk around the store with for an hour. Put back.
Get a cart and put a 2 bags of cement in it. Walk around the store for an hour. Extra Points: Put a couple of lead pipe joints in your pockets. Put back.
Buy one item at a time for an hour. The walk back and forth from the store to your car is great for the cardiovascular. Extra Points: Return items to store in reverse order same day.
Look for a straight 2x4. This can easily translate in an hour of stretching and lifting.
Tip: If you can find one buy it.
Walk around store and look for someone to help you. Believe me this will take an hour.
Authors Note: Not only did I lose 5 pounds, I was offered a job in the plumbing department.