Make one using materials sourced for free.
One option: http://www.instructables.com/id/Build-a-Milk-Crate-Cart/
Another possibility, go to a gas station/grocery store see if they'll let you have 4-6 milk crates. Fasten crates together. Could use plywood for a base under the crates. Get some pneumatic wheels from 4 disused wheel barrows and put a handle on it. If you can do it w/ freely sourced material, won't cost you a plug nickel!
Check craigslist free stuff, freecycle.org, ask neighbors, friends, relatives if they have some stuff you can dig through. Could make a mondo one out of 4 car spare tires (if the price were free, why not?).