Hidden in Lysterfield Lake Park. Everything you need is contained within the 4 supplied BMPs. (Note: They are displayed at 25% of full size).
Click on each letter to download the 4 BMPs. A B C D
The links are Dropbox links. You should be able to do a direct download to your PC without having to set up a Dropbox account.
The cache is a 1 litre Sistema container.