Liklik balus. Your post#3935
Bob Bates of Trans Niugini Tours, Mt.Hagen, flies his tourists from Hagen to Madang on an irregular basis in his PAC 750. You may be able to come to an arrangement with him to drop you off at Goroka on his way back to Hagen if he has a flight that fits in with you schedule. Trans Niugini Tours has it's own web site. Their Hagen number is 5421438.
John Cheung, of Island Air, Madang, could take you up in his C206 but that would be expensive.
Airlines PNG has daily Dash 8 flights POM-GKA-POM according to their October 2013 schedule.
If you want to get from Goroka to Hagen you could catch a PMV, (not recommended), or you may be able to hitch a ride on one of Doug Sharpe's trucks running regularly from Lae to Hagen. Doug runs Wagi (his spelling) Valley Transport Ltd. based in Hagen and their number is 5451333.
Hope this helps.