I remixed the router attachement user meirm made -> http://www.thingiverse.com/thing:31254
Just screw it onto yout router an adjust the depth of the routerbit.
I made the frame wider to achieve a better rest at the work piece.
I added three holes so that you can screw the attachement (with M6 screws) to a acrylic glass-plate oder a piece of plywood if you need a bigger base area of the router.
You need two M8 screws with a truss head and two M8 bolts for the handles.
I printed the parts with 0.3mm layerhigh with PLA.