Welcome to ECF. Ex-army here. When I was in, way back in the olden days, smoking was actually encouraged. I used to live in Cruces up until January. Anyway back to your question. I'd suggest a 510 with a white battery if you want it to look like an analog and still give a good hit. Use a carto and it'll be about the same size. Litecigusa.net has them, and white atty's too if you want to go that route, and they're cheap $9 for the batt and $6 for the atty:
Joye 510 Manual Switch Battery,
Joye 510 Atomizer. You might be able to find a complete white setup somewhere too. Then you'll have to learn how to stealth vape which is actually pretty easy, just take a hit into your mouth, inhale it and hold a couple of seconds, then breathe in deeply through your nose and hold it a second, then exhale slowly. This will give very little or no vapor after a bit of practice, not that I'm trying to help you get over on sarge or anything.