Run a search for 30 X 18 sink grid. You will find a lot of options. Link has many and seem to be a good price. The location of your drain may have to be "eyed" for size. Also, the grid shouldn't be forced in, so anything a bit smaller in size.

Here is a link that might be useful: sink grid

I used to use a smaller bath mat in the bottom of my dog grooming sink so the pups would have easier footing. I have tossed it so can not measure but the sink is 2 by 3. It was smaller than that. I had to carefully cut a drain hole. You might be able to find a bath mat in the color or non color you are looking for.