The importers buy them still covered in cosmo, then distributors buy them from the importers. Not much you can do about it. However, most of the Mosins that come through my Big 5 are clean - usually a little bit of cosmo in the inner works, but not covered in gunk. 'course, I've also seen some that were literally dripping with it, including one poor M44 with a completely stripped and weathered brown-grey stock that I'm petty sure was in the middle of pulling campfire-fuel duty when the Germans mounted a surprise attack and effected its return to its intended usage.
Buy from a private seller if you really can't find any around there that aren't fairly clean, but expect to pay more, because nobody else likes dealing with it either. If the stock is clean, it really doesn't take that much to get it off of metal, so you may want to just look for one with a clean stock.
