It is great
I don't think you need the larger size. I have two and the regular size is perfect. I hose the grass down (really well) and let dry in the sun. It should last a long, long time. I do put wee wee pads under the grass though to collect the pee.
There are different brands:
www.doggiepotty.com
or on ebay:
dog potty, great deals on Pet Supplies, Art on eBay!