If you can't find round stock and have a jigsaw you can make your own easy. Buy a ready made cutting board, make a pattern the size you want, trace and cut. After checking the fit and sanding the cut edges seal with food grade mineral oil if you choose wood.
The Tuscany we used to have had a double sink and two covers. I used one of the covers as a pattern and sawed out a nice looking butcher block board. Looked good and worked good, no more having to drag out cutting board. Also the lip on the under mount sink held the board nicely in place.
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