One of my jacks was leaking really bad, so I took it apart to replace the 'O' rings.
One part stripped. It's the pump cylinder, and it is made of light aluminum.
I have the jack at a local machine shop, they are going to make replacements for that part for all the jacks. The new parts will be stronger, they are making them from brass.
If you have a jack similar and need this part then let me know, I can have them run off more.
It seems to be a pretty obscure jack, I can't find a name or parts for one like it online anywhere. But these parts will be better than the original components.