I don't remember where mine came from, but it was mail order. With shipping, it seems like it was about $15.00.
Since then I have found another, possibly better, source. McMaster-Carr. They are a mail order only store. After finding it at McMaster-Carr, I checked Granger with no luck.
There is a whole range size of these things. They are used for packaging. They are especially popular for shipping various small parts of one kind or another. They are also sometimes used to ship tooling to machine shops.
Here is their web site:
http://www.mcmaster.com/#
You will find what you are after under shipping supplies then tubes then adjustable length tubes. I think the one you want is part # 2108T42. Typing that part # in the search field at the first page of the above link will take you directly to it.
You can see there are other sizes if you want to try something slightly different from the one you already found. Be aware that you need to drill a ventilation hole or two or three. Mine came with one and I added two more on the other end.
McMaster-Carr is a stand up company, well liked and respected in the business community. The only negative to ordering from them is that there is no way to know the shipping charges until they bill your credit card. The businessmen I know that regularly order from them are not worried about the shipping charges so I'm guessing they are reasonable. You might want to try calling them before placing an order.
I'm considering ordering two more, one that would be a better fit for my small travel brushes and one that could handle my Beasts.
Art supply stores also have sizes of tubes that can be cut to size (length) but the pharmacy tube or the spice container are ingeniously cheap.
I went a different DIY route though :
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