I'd usually approach the local water softener company; verify that they repair softeners and deliver salt locally, then ask what they sell.
the components are widely sold and many are made by a major international company, to be assembled by various makers, so it seems to me that a reputable local company will be selling a product they are happy to guarantee and service.
I am currently using a reconditioned Permutit from a local specialist, because the price was very attractive compared to having my old Permutit repaired. There is only one assembly in it that has any moving parts.
(the Permutit company went bust some years ago and the trade name is now used by another company, it may not be of the same standard).
IME they go for about 10-15 years before the seals wear or jam and need repair or replacement.
Lots of people like the Harvey, though it is rather expensive. Companies that advertise in the Sunday papers, or sell door-to-door, tend to have rather high prices.
There are some very cheap machines sold in the DIY sheds, you may find that local specialists are unwilling to repair them.
BTW my reference to salt delivery is that if you carry salt in your own car, a single spilled piece can rust a hole through the floor. Look in the salt delivery van and you will be shocked. If you find a local supplier who will sell and maintain your machine, and deliver your salt, I hope you will be as happy with them as I have been with my local company.