Not sure what OP was looking for, and I can't find it now on the website, but Matfer used to sell actual deep cake pans (not sheet pan extenders), both rectangular and square, that came with dividers that you could reposition for desired portion size and shape. They resembled this cheaper one on Amazon. I don't know how well this one would actually work, but I used to see a lot of these. I wonder if the reason they seem rarer now is that they didn't work great. Maybe they did, I never had one to try.