Hutch, PVC tubing works but will soften. A piece of pipe or EMT tubing will work. Seal the ends with something, wood, tin foil or whatever. It's not real important that it's sealed up air tight. It just needs to keep the interior hot and humid. I've used aluminum duct tape, tin foil folded over a couple of times along with hose clamps, bungee cord and zip ties. Almost anything works? I've also heard of people using bath towels to wrap the wood up and then pouring boiling water over the towels to keep them hot.
Dave