you could look into a bottom feeder. a vmod specifically if you need an out and about PV.
Mine goes every with me, even to the bathroom
i find that it takes the best of what tanks offer without it leaking on me at all. though, like most bottom feeders, you'd likely will end up using an atty on it. you can also use a carto on it if you prefer them.
here are my personal generalized pro's and con's though
~tanks
-- pros
holds extra juice to vape
can use any cartomizer on it with a punched hole (punch your own)
some are aesthetically pleasing. very very aesthetically pleasing on my eyes. (different colors, styles, metals).
cheap(er then a bottom feeder set up.)
various sizes to accommodate your vaping needs (2.5mL~8mL of extra juice)
-- cons
they can leak
"spinny" and can slip off easily
feeding the cart will depend on how big or how many tiny holes you punch in your carto
will not fit all mods; it can block air flow in some mods
strong cinnamon juices will crack some tanks; making them leak and eventually break.
hard to fill back up unless you get the very expensiveness tank systems with a hole and screw in the metal for easy feeding.
~carto's
with a good carto, it can last hours before you have to top off
very cheap to replace
easy to fill
no fear of leaking
come in different sizes as well (standards, xl, mega, mega xl)
will fit all mods with non-proprietary connections
--cons
so many "knock offs" it's hard to keep up with what's what. so with that said, lots of weak cartos out there. same for atty's however.
smaller carto's will need to be topped off more
poly-fill taste/cart taste
easy to break if your not using proper tools to punch holes in them for tanks
to add on;
~atomizers
--pros
great pronounced flavor, more so then carto's
more vapor on a 3.7 device vs the carto counter part
more throat hit
performance-wise; it beats any carto (assuming your at a standard voltage when comparing)
can be as cheap as carto's
--cons
cheap atty's dont last long at all and you can go through 3 in a day if you chain vape like i do
higher-end models like i06's and hh.357s need proper maintenance to last long (weekly vodka baths; 1+ year atty)
you can pop the coils more easily
very harsh dry hit when it's dry
you need to top off atty's more unless used in a juice feeding device
can easily get flooded
no proper maintenance leads to a dead atty within hours (even on cheap atty's)
can leak very easily if over dripped
~clearomizers
--pros
you can see the juice (like with a tank)
self contained system
bottom coils (are what i'd go for)
--cons
very little juice can be filled in the smaller sizes
most can break easily
condensation was a big negative with me (problems of a top coil clearo)
after a while, my juice taste like crap.
will not work with 100% vg.
i won't list specific model pro and con's because those are specific up's and downs of those parts. these are just my generalizations of what i've had experienced using my equipment that i have.