Rare skeleton shields?

I'm wondering where these prominently drop. I wanted one of these for a while, shadow shield is nice, but skeleton is nicer especially w/ the upcoming armors, anyone got an advice?

I'm pretty sure sure skeleton shields drop all the time in the ToPK. But they almost never have good bonuses on them. Usually just 15 or 16 armor.

I see them mostly in the southern shiverpeaks area and sometimes in crystal desert. It's been a long time since I got a usable gold drop though.

I think people get them from chests... anyways I bought -2/-3 stance/hex with 8 req for 1k beat that

I've seen blue and purple Skeleton Shields drop in the Underworld recently.
They've always seemed to drop for me in the Ruins of the Tombs, never seeing a Rare one though.