Could always get a holster ??
https://i.pinimg.com/736x/b2/81/4b/b2814b3df8302dc74d48412baf1ac314.jpg
Found this, they're silicone and work up to 19mm tanks. But I don't see why you couldn't stretch it to fit tight as hell on your wider tank, I wonder if it would be tight enough to hold the weight of the mod if it was to fall... Could be worth a go for £2.
https://www.ebay.co.uk/itm/352725350928
That there is the stuff that dreams are made off! Need to get me one of those [emoji1303]
Yeah a holster with a Smok Mag mod then you can be the fastest vape in the west.