Hello Iris,
I've only now read your message, so my reply may be too late, but in any
event here it goes.
Instead of buying a baking stone from an expensive gourmet goods store, I
went to a stone vendor (i.e. one that sells custom-cut marble and granite
for flooring, countertops etc) and had them cut a piece of the cheapest
granite exactly the size of my oven. It works beautifully and was much
cheaper than the "official" baking stone sold at the local gourmet goods
store in a kit with a stupid little peel for a small fortune). Granted, I
live in Brazil (where baking goods stores simply don't exist), but perhaps
you could look into this alternative?
Best wishes,
Erik