I recently bought a set of pinball dolly lifters from a guy called hi tech tony on ebay.
Here's a dead auction - but they keep coming up as he makes them
http://cgi.ebay.com.au/Pinball-Trolly-Lifters-Dolly-Movers-Set-of-2-New_W0QQitemZ320481035131QQcmdZViewItemQQimsxZ20100129?IMSfp=TL1001291710001r18152

On flat surfaces these are a godsend. I can re-arrange machines in my gamesroom on my own (and even wheel into the house) & really helped when I purchased my last machine which was a flat load.

andrew