I was also looking for a dual battery squonker. I was looking for mech but didn't find anything that I liked. Anyhow I tried the squonk Genius Adapter.
Squonk Genius – Squonking on Any MOD – CTHULHU MOD -Top Innovations for Vaping it goes with any mod / BF RDA combo. It's my first squonk so I can't compare with a real squonk.
It a bit finicky. Since it's not a full enclose bottle it's more of a plastic cylinder. The whole adapter is the bottle. So at first I press too hard and pop the top seal of the plastic cylinder. Easily solved by unscrewing everything (actually open the adapter and not just removing the mod) and reassemble but I didn't know it and it wasn't sqonking anymore. I had to wait until I was home to open everything. So now I don't press too hard. When you know how you don't need tool just unscrew the top part and fix the seal and re screw the top part.
Also It has a solid floating pin. However when your RDA is on nothing move. With the RDA off I push my pin up as far as possible Then screw in my RDA by doing this the pin is push back down and you have a perfect contact. Otherwise the pin may be too low and not have a proper contact.
Here on a staked tube with pulse 24 RDA on top
Here on a El Diablo Satan
I only have it for a few day but so far so good. I love squonking.