Does anyone know of a shop that can make a simple flat top/plancha for me? I'd want something made out of 1/4" plate steel with three legs on it to sit inside my Big Green Egg so I can use it as a flattop or to cook pizzas on. I can find all the pizza steels I want, but I want something with legs so it's easier to get pizzas on and off of a peel. Thanks in advance.

Have you checked out what Ceramic Grill Store has to offer.

I skipped the BGE plate setter and went with their XL Rig and adjustable woo combo.

I think this will fit your needs nicely.

I think I found what I was looking for, but I'm not sure it's going to get hot enough.

ETA: their griddle/plancha seems to be what I want, but it looks like it sets down in the cooker at grate level. I'm looking for a griddle/plancha that sits more at the felt ring level. And I don't mind having to burn extra charcoal to get it hotter; it's not something I'm going to do very often.

Maybe Metals4U ?

If no welding required then yeah just go pick up some plate. Cold rolled plate will have a nicer finish with no mill scale. Hot rolled plate will have mill scale on it - but it's ok to use.

I use 2 pieces of 1/2" hot rolled steel in my oven for pizza (2 because one piece is too heavy).

Metals4u will sell by the foot. If you want it round you can diy with an angle grinder. Maybe drill a hole or two for removal, etc.