I found this, not sure if it would work for people? Also it is expensive but I think you would need to go and view to see if it might work for ballooning.
They come in three sizes.

http://www.nisbets.co.uk/Rubbermaid-Hou ... il.raction

Looks interesting. I watched the Youtube video. Not sure the wheels would work on grass. I often have to drag my trolley into the middle of a field. If you get one, let me know if it works for balloons.

This is the cart on an American site, not sure if it's any cheaper.

http://www.rubbermaidcommercial.com/rcp ... oducts.jsp

Another variation on the trolley, http://www.mobile-pack.com/