I just got the new ad from Harbor Freight and they have the cargo carrier on sale again. It's one of the ones that uses a standard 2" receiver hitch.
It's one of the nicer one piece designs, 20"x60" and can carry 500 lbs. The price right now is $40 until June 23 at the stores.
I picked one up the last time they were on sale and they are pretty nice. I did have to take off the rear bolt-on rail to clear my spare tire though.
is a link to the item.