I know this isn't an answer to the question here but it may be useful.

One time I made an IV bottle type of fluid reservoir for a hydraulic jack
that allowed the jack to be used in any position. I used a short piece of
PVC pipe and fitted it with a tube fitting. I also made a new fill plug for
the jack and drilled it and soldered a tubing fitting on the plug. I
attached a piece of tubing between the PVC pipe reservoir and the jack,
added hydraulic jack oil and then (the hard part) did my best to get all the
air out of the jack. The idea is to remove the air and completely fill the
hydraulic jacks internal reservoir so that air can't get to the pump. The
external reservoir then supplied the oil for the jack's ram displacement.

I hung my reservoir on the wall near the press I was using it on but it
could be designed to set on the floor. I think I could have improved on
removing the air from the jack with a brake bleeder vacuum pump kit but I
didn't have one at the time.

RogerN