I don't think I can help you directly with trading since all of my toons are too low for your level, but I can give you some advice on how to get them yourself while you wait. Well...actually just the Foe's Ring since the Ring of Magical Dullness can just be found as basic loot in 5-1, so I recommend just searching a bit for that.
Unless you're dead-set on staying at Pure White Character Tendency, simply kill non-essential NPCs until you're Pure Black to start the quest for the Foe's Ring. Obviously non-essential differs depending on your build, but basically just off any merchant who doesn't sell anything you'll need or characters like Urbain and Freke's Disciples who become worthless once you rescue each of them. Once you've hit Pure Black Character Tendency, it's only a matter of freeing and killing Yurt, then going along with Mephistopheles until you have the Foe's Ring. I'd recommend trying to do the quest before starting a NG+ because otherwise Mephistopheles will have you killing off alot of important NPCs really fast.