I bought 2 of these to use as the tray (which I line with pee pads)
White High Impact Styrene Tray - US Plastic Corporation
I bought a 2x5 roll of this over stock first quality grass (that was the smallest they had to sell)
On Deck Sports - Buy Cheap AstroTurf for sale. High Quality Turf for a bargain at OnDeckSports.com
All in all I spent about $60 and had to cut the grass down to size
