A little addendum regarding the igo-s - nice vape but wasn't very pocket friendly at work. The o-ring arrangement didn't hold too well and the top cap popped off a couple times.
I believe that's a common problem with those. If you can't find better o-rings to fit, I have a fix for you. Take the o-rings off, wrap the base with some teflon thread tape pulling tightly to stretch the tape, replace the o-rings and cut off the excess thread tape. Worked with my Igo-L, till the 510 threads wore out that is.