Here's a solution I found while living in Vermont. I went to Long Acres in Lebanon, NH, looking for unglazed quarry tiles and instead came home w/ a $2, 22lb blue slate paver. It is almost 1 inch thick, sat on the bottom rack of my stove, and heats up (and retains heat) quite well. Much better than those 1/4 inch thick pizza round stones. Not to mention, I've heavily misted loaves before and this doesn't seem to think about cracking. The garden center had lots of sizes to choose from so I just measured the base of my oven and got one to fit. I now have an old gas Magic Chef stove, and it fits right on top of the metal plate which hold the heat element, so it works even better now. My oven spring and consistency of baking has improved a lot.