Those guides get really booked solid for that time frame. One guide you might try is Bob Worley (Clackamas Based). He is one of the qualified Deschutes river runners, which is gonna be required in the low water in Sept. There is also River Bend Outfitters, Homers sporting goods, Jack Smith, Youngs guide service in the Dalles..September is also good at the mouth with those Idaho B run fish and the crowds start to drop as you get further into the month.