Submitted this to hackaday but maybe it's more interesting here.
A cigar tube from ebay (this one cost about £6 and is made from thick, polished, welded stainless steel) is a good length to hold a TS100 soldering iron in a portable repair kit.
You can put it away hot without removing the tip, or use it as a heat-proof rest while in use. This twin tube has room for solder, too. A spare tip will fit down the centre of the solder reel. The TS100-specific storage cases I've seen are more compact but require you to wait for the tip to cool and remove it. I leave the clamping screw loose but that still seems a fiddly solution.
Cigar tubes with one, two or three-cigar shapes provide a choice of space. My toolkit also includes a length of silicone cable and an HP travel adapter offering both 20V at 65W to power the soldering iron and 5V USB for projects in a small and light unit. A USB power pack with a 12V output can also be used.
Improvements might include a heat-resistant silicone lining to avoid rattling, and a similar setup based on the TS80 and USB3 power.
https://drive.google.com/file/d/1F48V11BMtx--LpqLeQiHLFiTbLp2NKbl/view?usp=sharing