You wont have any probs in Sydney,use to live there.Definatley have good gear there dont worry.
I use to travell around Australia for work,every city i stoped at i managed to find pot before the days out.Most people will help you out if you are cool about it.
I would be suprised if you couldnt get any in Byron bay but if you cant head towards Nimbin about 45mins from Byron this is hippy central the town was built on the stuff.
If all else fails i live on the Gold Coast about 1 and a half hours away.You can look me up if you need to email me.