How do I obtain a second ring that's 170. The highest item level I've seen from a dungeon is 160 and I can only have one of the rings purchased with Tombstones.

I can't do but two dungeons until I get item level 170, but it doesn't appear possible to get that unless I can find a second ring. By the way, I haven't yet bought all of the Tombstone gear... I'm still working on it, but I'm pretty sure that if I'm lacking a second ring, it'll count against me.