I had a 6x3 vinyl mat printed for me by Bannersonthecheap.com. It came out to 33 bucks shipped to Canada. I found an ESO picture that I liked (you can use high res hubble pictures, whatever), edited a bit in Photoshop to make the contrast pop a bit more, and I sent them the picture to print. Got the mat in 4 business days. I cannot recommend them enough.

You can get a 3x3 for about 15 bucks plus shipping. For the price of one mousepad mat, you can have 5 vinyl mats. I admit the mousepad ones are nice, but not for that price difference.