Kampfstiefel are only issued to members of the Swiss Armed Forces or members of Civil protection. It is not possible to buy a new pair. You can only obtain a pair of used ones, which i would only recommend if you want to use them for work e.g. on a construction site.
Theres a lot of ordonnance Kit from our Army on these sites. The stuff that is there legally is no more in use with the Forces( there are "Liquidation Shops" run by the Army which sell that stuff too.) The illegal stuff is that which is still in use with the Forces. It is property of the Army and the so called personal equipment (Kampfstiefel being part of it) is issued to soldiers to store at home until they are next called to service.