Go to Mel Senshir, and save your game. Then, kill the Dokkalfar merchant to the left of where you spawn. Pay the fine or go to jail. Go to one of your houses, and sleep for four days. Go back to Mel Senshir, and the Dokkalfar merchant you killed should have respawned with new inventory. You can now buy a new backpack. Repeat this as many times as desired. Note: Try killing the merchant close to where he is supposed to be since when he respawns he will appear wherever he initially dropped.