The ring of Wizardy that you can "find" from the Harpers is during the first confrontation with Galavary.
If you've done the quest where you rescue a harper and bring it back to the hold, and then the subsequent quest to help Xzar find his thieving friend, you'll be able to get a series of quests involving the Harpers.
The first one is where Jaheira is called back to the Harpers alone, then she'll come back the next day and ask to bring the entire group with her. If you go with her, you'll be forced into a fight with some Harpers, one of the wizards drops the ring. I think it's the male one.
Needless to say, you need to have Jaheira in your group for this to work, and no you don't have to romance her into it.
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