Credit where it's due, silver is the most difficult metal to find.
That being said? None of them are hard to find.
You don't like the wishbone? You could always try the sledgehammer trick (iron or stagbreaker), where you smack the ground where you *think* silver might be and look for "too hard" that indicate the exact location of a vein.

i had a *much* harder time finding the Vegvisir runestones for Moder and Yagluth.