Hi Mate
Sorry cannot offer you a Job as I am only a Instructor , But here in QLD most dive centres will not offer paid Employment to DM's as most of them will work for free here (bit like slave labour) and then if there is a Job usually it's from a DM who did the course with that dive shop.
I do Know a few DM working but they get max $50 a Day ( less than $5 hr - I still don't know how this is legal) even Instructors only get $100-$120 for 10-12 hr day $10-$12 hr under the legal min but the dive shops get away with all this as only employ casual and have always more Dm's than they need.
I suggest you just get List of all the Dive centres in a Area you would like to work and email them That usually is the best way , as if someone left recently (dive industry has a Quick staff turnover) you might get something, Couple places in Cairns/Whitsundays is always looking for a DM to take photos of customers then sell. No salary but commission usually.
Otherwise Non tourist areas usually only have work on Weekends - Always a good way to get experience, pester your local Shop for anything going even if only sitting in the shop or filling tanks as once you have your foot in the door that Helps , Otherwise Online Jobs (PADI website pretty good if you are PADI)
best of luck
Mark