They are generally seen in toy libraries, in the game industry, and in fairs and shows. I’m aware of neither reseller nor site offering these objects: giant abalone boards.
If you are interested in purchasing an oversized abalone board, you will find a used one here, for the trifling sum of 295 CHF (Swiss francs), about 242 €.
Ok, it’s not what you’d call cheap, and regarding the colours, I saw best combinations. But it’s really the first time I saw one on the market. And for that price, you also have the proper pedestal.
Still, the oversized abalone board in rosewood, which was available for about 150/180 €, was certainly more elegant.