After some reloaders experienced primer ignition issues in 2010 with Wolf SP primers (silver/nickel colored primer cups) with the claim of harder primer cup (not with Wolf LP bronze/brass colered cups), Wolf SP kinda disappeared from the market place/gun shows.
In 2011 another brand called "TulAmmo" began selling primers and loaded ammunition in the USA. As far as I know, both Wolf and TulAmmo (or "Tula" called by many) are manufactured in the same Murom munitions plant in Russia. I am not sure but some PMC primers (at least the Non-Toxic primers) may also be manufactured in the same plant under contract for now Korean owned PMC.
Unless you can find some "new old stock" (NOS) Wolf SP primers, your best bet may be buying Tula SP primers, which in my opinion, is essentially the same.