I want to bid on a part for a floor washing brush. The company made a
bunch of PVC tubes 1" ID X 1.375 OD x 12" long. It's covered with a
material that looks like carpet...'kinda. It works great until it gets
hot then it gets bendy. The company's lab came up with a fix that
involves a taking a Derlin tube that's 1.040" OD x .75" ID x 4" long
with a .312" slit along the side and pressing it into the middle of the
12" tube to act as a stiffener.

What's the cheapest way to make these? Is there a better solution?
They need 10k+ of these. They will supply the Derlin material.