ShopNotes has plans for a couple portable router tables you can build for a reasonable cost. You can even get them as a download from
www.plansnow.com
You might want to look at the Router Workshop table from Oak Park. It assembles with plastic locking couplers and can be knocked down for easy transport or storage. Find a link at the top of our pages. I use my Router Workshop table clamped to a pair of sawhorses and it is perfect.