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If you look for Large Professional Bakers Dough Couche for baking Baguettes on Amazon, you'll find one that's 35x26" for $10. Most won't run more than $15.

That's just what I was going to recommend. I have a couple of nice ones that I use for my baguettes and I think they are just as nice as the 3" that came with my Scruppleworks and Neil Miller strops....