ACTUALLY the Arms Dealer will sell Silver Bullets in earlygame during a Blood Moon. :V
I'm PERSONALLY against having an alternative for silver bullets, because the bullets aren't made of silver just to be made of silver. Silver Bullets are a mythological reference. They're supposedly holy in some way. There just isn't anything like that about Tungsten...
Granted, you can't craft silver bullets in a tungsten world, but as I mentioned you can still buy them from the Arms Dealer.
If so, why silver bullets don't deal extra damage against werewolves, like stakes do against vampires?