Dina, I have a rectangular pizza stone that I bought from Sharpknives.com some years ago. It is a really great pizza stone. It is better than most of the ones you find in the stores. It is more like a quarry tile. I paid $25.00 for mine. I can't find it on their website because they redid their website. But I found it on another site. Here is the link: http://store.yahoo.com/p4online/bakingstones.html
arrow down the page a bit, till you see the 14 x 16 rectangular one. It is really a great stone and even better, I can put it in my cleaning cycle in my electric oven. When I first bought it, I asked the owner how was the best way to clean it. She suggested I use the cleaning cycle in my oven and even told me, if for some reason the stone cracked, she would replace it. I've had mine for 3 years now and always clean it with no problem in my oven. Again, like mentioned previously, if you don't want to spend that much money, the quarry tiles are your best bet. One more thing, if you buy a pizza stone, or quarry tile, make sure you never soak the tile in water, just wipe it with a sponge and scrape it with a scraper if needed. If it does get a bit wet, make sure it is completely dry before you put it into the oven or cleaning cycle or it will crack.