Or you can make one yourself.
Buy a quarter thick plywood at Home Depot. They are usually sized @4'x8'. Just ask them to cut it down to the size you want. I bought the one with the white laminate on one side. I tried it for a few months and it just collects dirt and dust since it's white and all any dirt is visible, so I decided to wrap it with a commercial carpet. It's one of those really low profile carpet where you can still roll your chair with ease. And so far it's been great. I used a 3M sticky spray and sprayed it on the top surface of the plywood then slapped on the carpet and nailed it down along the edges. And it came out like the picture below. Hope this help you with your problem.
I think i spent roughly about $30+tax on plywood, carpet, nail and spray glue. But it sure is sturdy and won't crack or get discolored like those plastic mats and it fits my work area.