Adding a Lean-to on the side of a building. Anyone know of a good kit?

try arrow sheds, they have aluminum ones. I am sure there are others. Tough shed comes to mind. If you are looking at wood, my neighbor built one himself. He found plans online and built it from there. Other than that its either customer built to the size you need or you will need to hire a builder . No escaping lumber or any material costs of any kind right now they are all rising.