I just do not know what type of pump to buy
I used a pressure demand pump that I bought at a Ford RV agency.
It did the job and it was low cost!
gas pressure delivery system
The farm service companies have been using carbon dioxide tanks with a regulator for many years to inject liquid fertilizer into the irrigation sytem.
I made one up a pressure fed high fructose syrup system which is a lot more heavy than stimulative syrup.
I only needed 5 to 7 psi to push the syrup out of a steel drum laid over on it's side.