Who is an Authorised Person who is able to witness your signature on your Notice of Intended Marriage?

The Notice must be signed in the presence of any of the following:

(a) if a party signs the Notice in Australia—an authorised  Celebrant, a Commissioner for Declarations under the Statutory Declarations Act 1959, a Justice of the Peace, a barrister or solicitor, a legally qualified medical practitioner (these include medical doctors & dentists only - not Registered Nurses), or a member of the Australian Federal Police or the police force of a State or Territory;

Suggestion: Police Office. All you need to do is visit any police station and they will be able to witness your signature.

NB. Witnesses can NOT include: Pharmacists and Registered Nurses. 

(b) if a party signs the Notice outside Australia — an Australian Consular Officer, an Australian Diplomatic Officer, a notary public, an employee of the Commonwealth authorised under paragraph 3(c) of the Consular Fees Act 1955, or an employee of the Australian Trade Commission authorised under paragraph 3(d) of the Consular Fees Act 1955. Note: For the definitions of Australian Consular Officer and Australian Diplomatic Officer, see section 2 of the Consular Fees Act 1955