Google ASC Pacific. Also, see if McEvoy is still in business, in
Victorville, or Bakersfield, Ca, IIRC.

You are not looking for "tin" sheets, but corrugated steel.

I used to be a steel erection contractor, and used to buy from ASC and
McEvoy. There are lots of what you want made in the US.

Check out local steel suppliers in your area. They might not stock them,
but be able to order them. Also check out roofers. Lots of people use
these for roofs.

Steve