At Christmas time the dollar store sometimes get the plastic mats in. If they don't sell well you can pick up a bunch of them for half off after Christmas. That's what I did a couple years ago. Kicking myself for not buying every one they had left. If I get low and desperate, I go to Walmart and buy them. They are usually $1.99 each and you can usually find some with a limited design on them. And I keep a lookout for them at garage sales too. They do come in handy!