Pretty cheap, can find them everywhere.

I use the 1/4 sheet pans most often because I do the majority of my cooking in my countertop Breville oven.

Half sheet pans for my standard oven.

Both at home and at the restaurant I use the Baker's Mark sheet pans*, they're $7.29 vs. $12.99 for the Nordicware, and they most certainly hold up to anything a home cook can throw at them. Of course, it's all a moot point if you want stainless; sheet pans are conventionally made from aluminum because it's lighter, which is no joke when you have a pile of 15 to lug around, and it cooks far more evenly.

If you want stainless you'll need to look a little harder, and pay a LOT more, north of $20 a pan. That's fine if it's your jam, but I can assure you aluminum holds up fine. The racks for the pans should be stainless, but that's for a different discussion.

* - https://www.webstaurantstore.com/2423/bun-sheet-pans.html?filter=size:1-2-size

I bought some stainless steel sheet pans and the first time I used them, I heard a loud noise and upon checking out the oven I noticed the pans warp out and become uneven.

I could never use them for anything else but cookies. I thought they’d be a better product but was surprised they were not.

I also have some other sheet pans that are probably aluminum, which is fine but cannot get them looking clean. I’ve tried elbow grease but alas they are still stained. If you know what products to use to restore them I’d definitely appreciate your input.

Barkeepers Friend or some other polish will usually work to get some shine back, but aluminum is soft and reactive so a patina is kind of unavoidable, especially if you just chuck them in the dishwasher like I do. All of mine are matte grey and a bit splotchy, but they still cook fine.

As for the warping, make sure you're buying 1-inch deep sheet pans, not flat cookie sheets, and that they have a wire rim (it should say on the packaging or listing); they need a little structure to not flex when they get hot,

Hope this helps, cheers