If I felt I needed one, I would just make one myself, rather than shell out > $1,000. But that's just cheap Dutch me!
In fact, I made myself a heavy-duty workbench on wheels, with shelves underneath to store most of my more common tools. I can and do roll it around the workshop. On the top I have metal shears and a big vise. I made holes to mount a shrinker or stretcher, and I can also mount my mini-brake (from Harbor Freight - cheap Dutch again). It works a treat and yes it is nice to be able to roll it to wherever I happen to be working.
This is the original version, before I added wheels and shelves: