Harry, here's my 2 cents. With your current setup you could get a flusher mount if you lose the bottle lid and use the nipple as the lid, they pull off quite easily. Onthe inside of the nipple there is a nozzle that a 2mm ID tue will fit on, probably other sizes as well as it is tapered.
On the outside tip of the nipple you can press/stretch a section of that silicone tubing on that is long enough to cover the tip and press tightly onto the connector's tube when the bottle is in place. Tight as it holds everything in place and is flexible for removing the bottle sideways. The connector you want securely mounted at that point as tension is key for this. I was quite happy with this on about 5 mods in some version or another. One strange thing was that if you leave the bottle out of the mod, the silicone tube would creep and pop off the nipple over a matter of minutes, but it is easy to not leave it like this.

Hope this helps.