It takes so little fluid...
Will a refilled 20 ounce water bottle fit in there?
Or
A funnel made from a water bottle?
Or
a wax paper funnel the length you need?
Or
A paper towel center tube?
Or
This if you're fancy
https://www.amazon.com/Foldable-Abso...400172&sr=8-17
Or
This if youre really fancy
https://www.amazon.com/Liquid-Fuel-T...6400318&sr=8-5
(I'm fairly sure these are 10 bucks at harbor freight. I use mine for lots of things)