Thershold 4000 "hydraulic magnetic breaker"

I have a little problem finding the right Magnetic Hydraulic breaker to a couple of Threshold 4000's from -78 and -79.
I have already done a full restoration of blown OPS, but those breakers (that have failed afterwards) seems to be some crappy ones that doesn't live longer than 35 years 😉

Does anyone know specs to look for, or do you know where to find the right ones?

Best regards

Figge