I just got back from Portugal where I bought a Cataplana. They come in many sizes. Most internet sales sites have a limited selection of sizes, but they are available on may sites like www.surlatable.com
They sell for:
Individual size, 6.5"
(Item #22223) $22.95
Set of 2 individual size, 6.5"
(Item #22508) $36.95
10.5" (Item #19540) $42.95
Mine is about 27 cm , basically the same size as the 10.5" and I paid 34 Euros for it, which is about the same price since the dollar/euro rate is falling.
I found your question while I'm searching the internet for recipes. I actually had the chef in the local resturant teach me how to use it.