Another product idea. I was just sitting here at the ordering page to pick up some more clearomizers when I thought, Hmm.. If I wanted to carry a couple of them with me in different flavors, would they be safe in my pocket or would I have to carry around my Vtube's carrying case and be encumbered? I have one of the Volt Carto Cases for the ease of carrying multiple cartomizers.. So being hopeful I went to see if they would fit in there.. not quite

Just a litttttle too short and a little too shallow. Which got me thinking about offering a Clearo carrying case, almost the same size as the carto case to allow 2 clearomizers to be stored in the case for easy pocket traveling. Would help keep pocket lint out of the tips or base connector, if there were a slight spill (which I doubt is very likely) it would also be confined to the clearo case. This way you could carry up to 3 Clearos at once (1 attached 2 in case .)
I for one would order one of these in a heartbeat for easy transport of clearos in a small protective case. You could even modify the Carto or (if produced) the clearo case to be able to accommodate both Clearo's an Cartos. A Clearo case that can fit two Clearomizers lengthwise, or 1 clearo and 2 side by side lengthwise Cartomizers.
Decided to break out my ruler and paintshop.. lol. On a whim, not designer standard here

Should be to scale though, unless uploading changed it.
-Standard Carto Case-
-Clearo Case-
As you can see, just fractions of an inch and you could use the case for Clearos and Cartos. If they were to be used by both, I would suggest going 3inches in length to accommodate two Cartos being laid out side by side lengthwise. I had an image I made for that design, but I accidentally saved over it and.. well yeah didn't want to do it again!

This would allow you to carry 2 extra Clearos, or 1 extra clearo and 2 cartos or 4 (maybe 5) cartos in a very small convenient case!