Hello,
I have acquired some useful maps for myself (in victoria) of my local area which i acquired of the local orienteering club. If you speak to one of the area you are interested in they may also be willing to provide you a map or point you in the right direction. Also maps they provide are very detailed and show contortion lines [sorry if incorrect name] (elevation, steepness) etc which can help you evaluate tracks before riding them or potentially highlight any which may be present?
Just my bob's worth.