Ideas to Fix or Replace Hydraulics on Trailer?

[BxB301]

I inherited an old trailer.
By buddy who owned it previously, never messed with the hydraulics, and the trailer worked as a trailer, thus he didn't care.
I would like to fix it, just so I can use the trailer to its full potential.
It looks like its has long weird cylinders connected to each wheel, fed via brake line, and a manual operated pump in the center.
I think you can raise or drop the trailer as needed. It might lay flat? or raise? Not really sure.

Look like the pump & trailer was patented in the late 40's
At this point, the pump is seized and does nothing. Parts are surely non existent.

Any ideas where to start?

 

[Eagle1]

Seen a setup similar on an ice fishing RV. Electric pump of course. That unit would lower flat to ground to park and raise to travel. Doubled as a toy hauler and made loading breeze.
I expect when pressure is removed the trailer should drop and pumped back up to ride height. It may have a mechanical lock for keeping it up

 

[BxB301]

Yeah, it does. They can be seen at the end of the cylinders in the 2nd photo.