The power cylinder is just your average hydraulic cylinder. A good hydraulic cylinder shop that works on construction equipment and such will have the o-rings and seals and will rebuild it. The company mentioned seems to be focused on the booster on the firewall.
Find a good old fashioned local hydraulic cylinder rebuild shop. Go there, take the cylinder, let them see it and look at the place.
I would NOT want to ship it off, you may never see it again.
The Ram (power cylinder) is available new because they were used on older Chevy full size and Corvettes.
Napa may have you covered with a cylinder rebuild kit, hoses or a new Ram. I searched 1963 Corvette for NAPA part. The rebuild with the seal kit ($10) can be an easy DIY project if you watch a few cylinder rebuild videos.
Here is a good thread from our Archives.
Be advised however, I am not familiar with the word "malfunbcrion"