First off, hello, and welcome to the forums!
As far as the O-rings go, most atomizers don't sell specific O-ring packs. Few do, but I don't think the spirals tank comes with any. If you know the inner and outer diameter of the o-rings you're looking for, you can get some from Fasttech, since they sell all kinds of parts including O-rings. I doubt you can find those dimensions online, so if you really wanted to know, I'd measure first the diameter of the atomizer where the o-ring fits in to, then I'd measure the thickness of the o-ring. Add the thickness of the O-ring (X2) to the size of where your o-ring goes to get the outer diameter of the o-ring. If you don't have a caliper measuring tool, I'd take the empty and dry atomizer to your hardware store and borrow it.