I have a small stainless steel vacuum flask, that came with a vinyl ' simulated leather' carrying case. The design looks ideal for a tamper case, just needs to be shorter. The case has a zip closure and a webbing carry strap. As the flask with case was $10, should be possible to get these made for a dollar or two. I reckon the neoprene wet suit material, with nylon on both faces for abrasion resistance is be an ideal material. Will post a photo later in case it helps with prototyping.