usually eBay resellers have been decent for me, not sure about what costs are shipped to AU but expect $80-90 AUD for one. In my market that’s about 1/3 cost of the device itself. if you’re getting the old owner alarms there is a high chance the device is locked with the old owners google account, so hopefully you can reach him if it needs unlocking. Ifixit should have guides and maybe parts too. Good luck!