I use a 5' lamanated countertop from a kitchen island with a cleat on the bottom so I can clamp it into my workmate.

I got it at the Habitat for Humanity Re-Store for $15..
Find your local Re-Store Here
http://www.habitat.org/cd/env/restore.aspx

The Re-Store sells donated building materials and leftovers from renovation projects.. Windows, Doors, Cabinets and so on.

You should be able to find a door laminate flooring, countertop and even cabinets to hold it all up.

A bunch of the wood working guys like a work table topped with Lamanate flooring.