i like HC's DCT 3.5 ml (?) tank.
3.5ML 510 DCT (Dual Coil Tank) Cartomizer MOD(1.5/2.0ohm)
absolutely no leaks from the tank. cartos battery hole is a different issue with leaking ;-) I've tried tanks from gotvapes based on the Royal Smokers CE series and they were crap. the DCT is cheap and it works great. tried and true design, rather than new and improved that are usually duds like their previous versions.
the stoppers on the end of the DCT are tight to not leak, but not so tight you can't remove. And Amy has spare parts for them cheap to keep you going