Ok, here is short guide how to do it.
First we need to shave off excess plastic from head of pump so wed have to cut less on device.
Next, since output of head is wide and usual air hose wont fit i found some bigger hose which connected output of pump with normal air hose (blue) which goes into aquarium. Some silicon is used to plug eventual holes and you can burn hose a bit for better fit (rhyme!).
Now see if head of pump fits in hole in device. Probaby it wont, so take a soldering gun and make it wider. Not TOO wide, it must not have much left-right movement.
Cut bottom of bottle so it can fit in device. Carefull not to cut too much or bottle will be too low and moving part wont push head. Cut little by little till it fits. After that connect hose with pump intake , that hose goes into fert container
Take some tape or piece of rubber and wrap it around bottle in device so it doesnt flip out when moving part presses head. Test device and see how much is in one squirt, mine was about 1ml.
If 40ml a day is too much for you (which is lowest i got) , you can maybe try to lower bottle so moving part wont fully press head and there will be less liquid in one pump action.
Alternatively, when buying bottle , look for one that have thinest piston in pump (spring is inside). The thinner piston, the less should be in one squirt