As said before, the first page of the user list (sorted by reputation by default) would be a good start, if you filter out those no longer active. Also the second page (not especially because Iām on it 
) lists some really active users.
Unfortunately there is no direct message functionality in OSQA, and no direct mapping of usernames to OSM either, though most people used (more or less) the same.
Maybe the simplest would be to ask a new question there, asking for volunteers and their OSM username. A quick check of their reputation would be enough to assume that they are trustworthy.
Or maybe just a thread here, why not linked from my āTips for power usersā post, to ask for the privilege, with reference to their OSQA account. Those who need it would easily find it, and an admin can just check their reputation there before granting rights here.
Hope this helps.