I have an Origen dripper that I use at home sometimes. It's like having two tiny cups of juice under your wicks, and vapes amazing.
But I still end up using it by dripping right on the coils most the time because; The caveat of an RDA is that if you are stuffing enough wick in the chamber and dripping enough e-liquid in there to last for a minute before having to drip again; it's going to leak out the side air hole if it's not upright. Period. Some give you more leeway than others, but there you have it; unless your willing to drip a lesser amount of juice, more often, it's gonna leak when tilted.
If you really want an RDA that never leaks and has 6ml on on-demand juice look into the Reo. A Reo is having an RDA without having to drip or over-saturate the inside of the chamber with puddles of leaking juice. Never leaks a peep. You squeeze the inside bottle, juice travels up to the deck and saturates the coil, then get's sucked back down. Everything else is left nice and dry and clean, except your coil and the tiny amount of wick tails you need inside the coil to hold the juice for a few hits.
Otherwise, your going to have to look into a RBA tank like the Kayfun. But they just don't deliver the goods and versatility that an RDA can, and your at the mercy of a wonky wicking/vacuum tank system that'll still on occasion give you grief like leaking, gurgling, or dry hits.