I have looked into getting one of these as well, however I don't like the 'square' ones, b/c I am thinking that as they turn the corners would bump into things on the table or hit you in the belly, LOL I also like the idea of them having a reversiable side to iron on. SImilar to the ones called, Brooklyn Revolver.
Here's a great idea I found and think I will try this way first:
Make Your Own Revolving Cutting Mat
CHarlotte Putland of Maryland tells how her husband make her a revolving cutting mat using recycled materials.
I had a large turntable made by Rubbermaid that I was going to throw away. It occurred to me that the turntable could be useful.
My husband cut a circle the size of the turntable from an old Olfa cutting mat. There was a raised lip around the edge of the turntable that would interfere with cutting, so my husband put a layer of styrofoam on the turntable to raise the mat to be level with the raised lip.
It works great! My home-made cutting turntable is much larger than the one you can buy called the “Brooklyn Revolver.” And the best part is that it cost me nothing to make.
If you want to make one of these revolving cutting mats, I am sure there are many Rubbermaid turntables available in thrift stores.