I'd call Wade Renfro out of Bethel. The Andreafsky is less than 100 miles from that hub. Might be able to find a native boat transporter out of St. mary's, but you'll still have to fly to and from bethel to reach st. marys.
There's local pressure on the fks of the andreafsky, but not many non-local hunters at all that I'm aware of. Easy river with shallow character, so motorboats might only reach certain areas.
larry