I actually have a Permutit, it's a reconditioned one that I got when the old machine went wrong. I understand the company went bust years ago and the name was bought up by a cheap company.
However
I suggest you call your local water softener company (there will be one). First question is "do you repair water softeners?" If the answer is no, try someone else.
Local companies will (normally) provide an installation service, repairmen and salt delivery as well as selling machines. They may be unwilling to service machines they did not supply and are not familiar with.
The mechanism is actually incredibly simple, there is often just one assembly containing all the working parts, a plastic salt bin, some pipes, and a pressurised cylinder, and the ion-exchange granules. My window cleaner actually built his own from standard parts.
In mine, the meter, timer and control valves are all the head made by Fleck, which seems to supply numerous makers internationally. I had new seals fitted to it and they are readily available and familiar to the local menders.
Many local companies will supply major brands, and also one of their own. If they've been in business for some years and have competent repairers they should be able to service it when required. IME this is after about ten years.
I'm told the cheap brands sold mail order and in DIY sheds are throw-away when they go wrong.
The companies that advertise in colour supplements and send a salesman to sit in your house until you sign up seem to be rather expensive. Like kitchen and window companies. They rely on most customers never having bought one before and not knowing what the price should be.
If you are in a hard-water area, look at your friends and neighbours. Ask the one with the softest, shiniest hair who she recommends locally. When you have a softener you will understand this.