Further to this deal, the KitchenAid mat at Costco is slightly cheaper but you do require a membership in order to purchase it. I'll provide actual dimensions shortly as soon as I can track down a tape measure. I'm standing on one as I write this and I can attest that it's quite comfy and excellent for a sit-stand desk.
Edit: I updated the price to the correct one. I've also confirmed the dimensions of the mat at 970mm long x 520mm wide.
2nd edit: They come in a range of colours, too: Brown, Black, Beige, Charcoal. Black must be the most popular because I had to lift a (very heavy) stack of them out of the way while Mrs. C tugged on the black one in the middle of the pile.
According to Amazon it's 20" x 38" or roughly 0.5x1m.