So I received the Vandy Vape Pulse Dual bottle from FT, and I am happy to say that it actually works fine right out of the box! It is a little bit fiddly to get the bottle in and out, but still much easier than taking in and out the original bottle. To remove it, place a finger through the squonk door and slide the bottle out. To put it in, align the silicon tube opening with the squonk pin and slide it in. Not as straight forward as on an ordinary squonk mod, but not bad at all. For me I think filling is easier using this more conventional method.
As you can see from the pictures the bottle does not sit as flush on the edge of the hole as the original bottle, so squonking is a bit more awkward. For normal sized fingers it should work fine, though. According to the product page on FT the bottle holds 7ml, which IIRC is the same as the original bottle. It has a bit of an egg shape to it, and it fits best with the Vandy Vape logo facing outwards as in the pictures.
Hope this helps someone. Unfortunately, the bottle seems to be discontinued, so grab them while you can. I ordered a six-pack from FT yesterday.