Topps tiles used to sell them. Think they're 450 x 450. Ceramic printed. They were rare even when they sold them so I doubt it'll be easy or quick finding some now. I remember the last batch or two in the company's 300+ stores being sought after because they'd chip easy and show the biscuit through which was clay coloured if I remember rightly. Used to see on the internal deliveries 1 or 2 tiles heavily bubble wrapped on a pallet on its own because a store in the North had finally found a store in the South with a tile from the same batch number.
So my first try would be to take a pic to Topps tiles.
