Before you go to look for a specific device, give a think about whether you'd want regulated or mechanical. The market that's available to us in the States has changed so much lately, I don't even know what's available to buy any more. If it's the same where you are, you could always consider ordering from Fasttech, if they have a good selection of squonkers these days. I imagine FT orders would get to you quicker than they would to us.
My favorite regulated squonker is a Revenant/TVL Delta (the kit, if you can find it, because the RDA that comes with the kit is great), and mechanical I'd have to say the Asmodus Pumper with an Elder Dragon RDA.
What squonking gives you that your sub-ohm tanks don't? A lot. Up to a 10ml juice reservoir, so no more constant refilling, the ability to customize your vape with a variety of coils (just about any kind of coil you can buy or make), portability (the increased juice capacity will last most vapers most of the day, or many days, depending), and I have yet to come across a squonker that was as much of a juice hog as some RTAs or sub-ohm tanks I've tried. Flavor and vapor amount, of course, depend on your build and your setup parameters, and knowledge of how well or how poorly certain builds work with the battery you've chosen to pair them with. And lastly, mech squonkers for durability. Many of them are so simple that almost nothing will go wrong with them. No boards, very little wiring, no displays, all you have to do is keep them cleaned really well at contact points and make sure you use good batteries.
