The HK mat is tiny. A good, big cutting mat (like Chad's) comes from sewing and craft stores. I like to have a big and small one at hand. A big one for big cuts (eg plane parts from foam) and a small one for cutting parts when assembling (eg cutting stringers from balsa).
So, after watching all the basic swappable videos I finally got some shots that showed a product code on the cutting mat: 97577. I couldn't quite get the product name but thought it started with a 'D'. Anyway, after some searching I found it: http://amzn.com/B004GXBXW6. It is a Darice 24" x 36" clear cutting mat.
In the end, there are many options, especially on Amazon: OLFA, Fiskars, X-ACTO, Dahle, Alvin, etc. What I really want to know is which one is the best bang for the buck ... I bought a 12x18 Fiskars one at Walmart and it doesn't seem to have any healing properties.
I also got the Hobby King one (yes, it is too small for foam plane construction) and it is a completely different kind of surface ... seems more like the OLFA one at Michaels than the Fiskars one.