I’ve had the same issue. The best one I found was the one I’ve attached below. It’s nice and heavy, does not warp, and feels like it heats very evenly from the thickness. I was able to snag a few on sale but still not terribly priced. Cuisinart AMB-17CS 17-Inch Chef's Classic Nonstick Bakeware Cookie Sheet, Silver https://www.amazon.com/dp/B000C1ZG6K/ref=cm_sw_r_cp_api_glc_fabc_3Uh.FbQ595TWH?_encoding=UTF8&psc=1