Cut a small length of 5mm hose about 8cm long and slide it over the outlet of your Pump, slide a T-Piece on the other end.
cut a piece of pipe that will hold your pressure chamber, cut out a notch big enough to fit the nozzle of the bottle in and then at the base of that cut a length wide enough for the hose, this will allow you to push the hose up and connect the pressure chamber later.
Now hot glue this to the outlet end of the pump with the cut section facing upwards.
Opposite the pump outlet connect the T-piece to the pressure chamber and a length of hose to the remaining connector; this will go to the trigger.
Now hot glue the neck of the pressure chamber in the support pipe