I know you don't want to make the tables yourself, but Jaime Hynemen has a pretty sweet expanding table design. I am sure you can contract a welder to do all the work for you.
The video mostly covers welding, but he show off the table close to the beginning, and then goes over the construction towards the end. May not look too impressive, but they are VERY functional.
http://www.youtube.com/watch?v=EA1jeViV4l8