I only buy the large size self-Healing mats. Largest size of it is 36", don't remember the other measurement. I have bought smaller sizes before, use them on the counter top in my sewing room for smaller cuts.

On Amazon, under art supplies they have lots of different sizes, and since they are sold as " art supplies" they are way cheaper ( but exactly the same) as " quilting supplies". I bought my 23" x36" pink/ blue cutting mat ( they also had black/green) and paid approx $40. Watch for free shipping deals, usually offered if you spend over $35.....

Cutting mats are also available at stores that sell art supplies or the ones that sell drafting tables. I have a white one that I've used for 15 years now. It doesn't have an odor to it like a lot of the other mats do and is stiffer. You can always turn a mat over unless you depend on the lines that are printed on one side only.