These seem to be heaviest duty pull behind that I have found. They are $$$ though.
Wikco Tow Behind Lawn Sweeper
I can't find my manual but I think it is made by Ohio Steel.
Hi fellas, I went and bought a Sears sweeper but when I got it home it was not the same as the display model. I called them up and the guy said he would swap it for the one on display. Just wanted to let folks know the store owner didn't even know that Sears had changed them apparently it had the same number.