This is the easiest thing to answer and it works and it's a friendly way to save your garden.
Buy solar lights! You can find cheap ones if you put your mind to it to go on a mission to find them. Bunnings have then all year round and you can buy "strings" of them that aren't xmas or ones in a rod to stick into the ground from balls, to butterflies. Even owls. You'll be surprised how they stay away. Also the blinkie ones. I lose no veggies or roses etc at all. They are nocturnal so lights can repellent them from getting near certain areas of your garden or string them into the trees that are bring attacked.
Just buy a say one string of lights, hang them up then budget for the next lot. They aren't really expensive at all. I buy string lights b,c it's more economical to do so. My garden, has least in the front but at Xmas heaps and out the back quite a lot and again not xmassy. A generic theme.
It's environment lyrics friendly and works a treat. Try it, all the gardeners I know use them. Owls singularly cost quite a bit and you just get one. Shop around!
We had a possum problem in our house. They managed to make there way into the roof. And that was a difficult situation. Outside of that, have you tried leaving a clear coke bottle of water on the lawn. I know it works for dogs but not sure if it works for possums. Hmmm....interesting problem!
Possums use our roof as a highway at night, however they don't dare venture into the garden because we squirt them with a little bit of plain water and they get the message in a kind but clear way. You just have to be there when they arrive and have the hose or spray bottle ready and waiting. Good luck.
All are welcome. No hoses, sprays, nets, lights or alarms here. I leave titbits of fruit out from time to time but nothing to get them dependent on us. I quite often wake up with one making it's funny noise outside my window.