Try contacting the legal firm who you engage to do the conveyancing for you. They may hold a copy of contract with a strata plan attached. The strata plan should show your boundaries. There should be no fee as long as they hold and have not archived or destroyed your file.
If, you are wanting the actual dimensions of boundaries you may be out of luck, unless council have a copy of approved plans...depending on age of constructions. Not sure if you will be able to obtain information without a fee.