they sell stuff like this at home depot - they're usually not very large. Also you can't lock the wheels but i guess tha'ts an easy enough mod to do. If you could find one that's like 20" diameter i guess it could work
yeah I have seen a lot of these at hardware stores. But Fiddler is right, you cannot lock the wheels in a position. Skater wheels are softer with better bearings as well.
I was thinking about maybe modifying it to a real skater dolly. I think the biggest problem with these are the overall design and cutting it to that specific shape.