I'm a chef, so I stand on these all day. As noted, restaurant supply will have a selection of them, these tend to be open-weave for cleaning, rather than the domestic ones which will usually be more of a flat mat style. Get beveled edges and put shelf liner underneath if on a slick floor. I don't like a really spongy one and I don't like the kind that interlock...the edges tend to lift in between.
Watson
PS...if you find something in the US that you want, I have a PO Box in MI, I could pick it up for you when I go.