Heartland sells
nicotine solution, or e-juice base with nicotine. Here's their
shipping info page. They do not ship 100 mg nicotine solutions, though due to postal regulations. Yes, you pay for shipping, hm, you pay to ship clothing too. *shrugs*
Like this but they only ship to licensed businesses
Yeah, and those licensed businesses need to hold a tobacco sales permit as well. It is along the same vein as ABC sales. The 'authorities' can yank a permit at a whim. "Got word you sold nicotine/tobacco to minors, no more tobacco sales permit for you. You'll need to reapply after paying the fines."
Bottom line the 'authorities' get kick back via taxes & uphold the 'public good' by limiting who you can and cannot sell tobacco product. Run afoul of those two things and you meet the zoot suits. They like those trendy jackets labeled BATF on their backs.
You may want to look into RDAs instead of Tanks or pods, use some kind of *ahem* real mod instead of disposables. I use RDAs with 18 mg nicotine strength based juice. Smoked 35+/- a few years at least apad, or more. Started vaping at 18 mg, not ever lowered my nicotine despite man using only 3 - 6 mg with RDAs. I do pretty well, cravings get met.
In fairness & honesty however, I'm a dual user. I also rub snuff. I know, the humanity, huh? Not ever been able to really kick snuff. Started again a couple years ago when bronchitis kept me from vaping. Still have days I only vape.