Good source for trunk floor panel?

1971 Duster: I removed my gas tank last weekend and discovered that the portion of the trunk deck supporting the back of the gas tank is about ready to fall off of the car (rusted under the spare tire). I have an estimate to have a new deck installed (16 hours labor) and I'd like to order the material this week. I recall finding trunk decks during previous searches - but would appreciate recommendations for a reasonable source.

Tx,
Ken