I built one using wheels from a couple of Trolleys from SuperCheap autos. The trolleys were ~ $25.00 each. They are the same ones as what you see at K&D and Bunnings, etc. Actually, the SuperCheap at Cambridge had the wheels for sale separately I think. I used the axles off the trolley as well. Didn't cut them down either - so If I need a trolley I can always put the wheels back on the trolleys !
I used standard skate trucks which I rejuvinated with some new rubbers. You want the stiffest rubbers you can get to avoid the speed wobbles.
Cheers
Marlon