Just throwing this out there, and I obviously don't know your husband, but it is possible that "sissy"/"tough-guy" are not exactly the right descriptors of his perception of the issue. It trying to appeal to his outlook, getting the connotation wrong could make you completely miss the target on solutions.
Even in working through my own outlook on vaping when I first started, I mistook the connotation of what I was feeling and thought that the issue I had vaping in front of other people was a fear of looking like a sissy. It took me a while to realize that that was not exactly right, subtle as the difference might be, and I couldn't even begin working myself up to vaping in public until I realized what the real issue was.
My issue is that I have an aversion to vanity, a quality often associated with "sissies". I don't like showing off possessions or in style. I don't mind performing a skill that I am good at with an audience, but I shudder at the possibility of someone thinking I am vain or proud. I like things plain, simple, durable, and honest. I drink my coffee black, beer from a bottle even in restaurants, when a box of doughnuts is passed around, I'll never take the one with sprinkles. I buy my vehicles in black, white, or gray, and have scuffed and painted over brand new chrome parts because I thought they were too flashy. Of course, I prefer simplistic styling but, if I'm being honest with myself, I have to admit that a big part of it is that I don't want to come off like I am trying to draw attention to myself.
I'm not all that unique. A lot of men that I know are like me. How this translated to vaping was that I smoked the same thing my friends did, namely simple cigarettes that could be fished out of your damp pockets, from a worn out paper box, be lit with a common lighter or match, and smoked without a second thought to method or technique.
Vaping gear, no matter how simple you make it, it infinitely flashier than cigarettes. Even if just by the fact that the have leds and clicking buttons. They are more complicated to put together and run optimally, and, when no one else around you is using them, using one openly feels like you're showing off. I still feel a little out of place around some friends, many of whom have taken up roll-your-own in an attempt to get a healthier alternative, and I'm the weirdo with the techie, gear-heavy solution.
I don't know what the answer is. When I find my solution, I'll let you know. Certainly, it would be easier to fly under the radar with if more people did it, but it's important not to confuse the issue with the popularity aspect. It is about needing to blend in, it is about not wanting to appear to wish to stand out.