I want to make a heat shield, what are your suggestions/ where can I buy sheet stainless?

Hi, I'm looking at putting a small vintage wood stove in a small room. It's about 12" wide and 20" tall with a 4" stove pipe. I'm reading that even with a metal heat shield I should have 18" of clearance from the wall, but the room is very narrow and I don't have that space. I have someone who can bend the metal for me, so I was thinking about having a 48" wide x 40" tall heat shield made out of two layers of stainless. 1" gap from the stove to the first shield, 1" gap to the second shield, and a 1" gap to the wall, with a 1" gap on the bottom for air flow.

What are my options for buying a standard sheet of stainless? Like 4 or 5' x 10'? I can brake and weld it into shape.

If that's not a good idea, what do you suggest?