And if those suggestions don't do it for you, check out a local gun shop- T/C makes tubes for muzzle loaders that are similiar to what you are describing if you cut them down. They run about 4-5 bucks for a three pack when you can find them.
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-IronRaven

When a man dare not speak without malice for fear of giving insult, that is when truth starts to die. Truth is the truest freedom.