I have a Braun Hobby EF300, or something like that, made circa 1967. Solid state oscillator.

It originally used 2 4V wet cell batterys. The manual shows little float ball tubes and filler caps like your item #26.

I found my ocillator worked (very slowly) on a 6V battery, and later once I knew the oscillator worked, and allowed the capacitor to reform, I ordered 4 2V gelled lead acid batteries (Hawker Cyclones) , and built a box under the flash pack to house them, as they did not have the same form factor as the original wet cell batteries.