I think spares etc. might still be obtainable for the k58 & a couple of other Pardini models which shared some common parts. I had a look on line & came across a fairly recently dated advert but have no idea about stock or availability.
I think they are a nice pistol & they don't seem to come up for sale very often. Maybe that's a good sign if owners want to hang onto them.....I'd be surprised if nobody wanted one but goodness knows where you would pitch an asking price. Maybe there's some old adverts you could use as a guide or perhaps someone on here will be able to give you an idea of value.