Stainless steel pipe offcuts (North Hinksey OX2)

I'm looking for various sizes of stainless steel pipes, or half pipes, that I can use for my art. They will go in a kiln so must be stainless steel with no paint or finish. I've got a couple that are 10-15 cm in diameter that were offcuts from wood burner flue installations but would love some narrower bits of pipe, maybe 4, 6 or 8cm in diameter, and up to 30cm long.