In the lakes around here, northern pike live with muskie, bass (largemouth and smallmouth), walleye, crappie, sunfish, perch, bullhead catfish.
Of those, the largemouth bass would be the best bet as a tankmate. They get large enough to not get eaten by the pike and they aren't overly aggressive. A bullhead would be okay too as long as it's big enough.
Sunfish make great aquarium fish but they would have to be full grown when the northern pike is still small to stand a chance.
I would go witha brown trout, You guys have a lot of them there, or like someone else said a largemouth bass would also be good, You should be able to get a hold of one of them in aus. Some types of snakeheads namely the argus would be fine with a pike. They like the colder water as well, or carp they can be found just about anywhere. Or if aus has any mountian streams the fish may be more like temperate natives in the pikes native range. Good luck, they are a really great fish to keep.
Im sorry my friend you may be dissapointed. These fish are going to be VERY difficult to keep tankmates with. I have not had any luck with anything and I have access to pretty much all of Michigan natives which is one state that pikes are native to.
Pike are particularly docile (like all esox). If any fish has the chance, they'll kill them. all sunfishes (Bass included) are out. Cichlids will almost certainly kill a pike. On the other side of the esox coin is their huge mouth and even larger appetite. Pike will eat fish 1/2 their weight if slender enough to fit in their mouth. Once the pike has completed it's growth spurt, I think a gar might work.
FYI...I'll bet a bullhead would shred a pike one quite night so catfish might also be out.
Sorry but it's a fine balance when it comes to keeping esox with tank mates.