TurboCommander AC690.
Try CommanderAir in Cairns. +61 7 4035 9808 or GAM head office in Essendon on +61 3 9379 1019.
They have flown out to the Solomons before (although that is further than 950nm? <img src="confused.gif" border="0"> ), and obviously have an international AOC. Limited performance data, can be found on the <a href="http://www.reefwatch.com" target="_blank">Reefwatch website</a>(their sister company). Go to the aircraft page, and scroll down.
Goodluck!