That seriously piss poor attitude of Charmilles is primarily why I have not, nor will I ever buy anything from them.
With that said, I may offer a small piece of help.
You can broaden you search for used parts, as all HS3100, 3600, 5100 and 50A machines use the very same powder brake.
Never seen the 70A so the complete assembly might be different, but if the above number you've listed is correct, then the powder brake unit itself is identical.