I'm with blueberryman- build your own from junk if you're handy and have a welder.  If you're rolling rocks you'll want pipe (doesn't have to be too heavy- mine's corrugated ditch pipe) with concrete filler, but if you're just doing your driveway with no rocks then something with lighter walls and water filler would be ok.  Trickiest part to finding the scrap would probably be the pillow blocks for the axle.  Lot less labour finding a used one nobody wants though, and that I can't help you with in your area.

edit- ever thought of asking a local dealer if they've got an old used one you could borrow/rent?  Depends on how often you'd have to roll your driveway if making one would be worth the effort.