I believe there's a Fetch App you can put on your phone that might work.
Contact Optus tomorrow and arrange a replacement. If it just stopped working then it will be free. If you busted it then its $10 or so.
Peter is correct that the yes tv app for fetch can act as a remote. The only problem is you need a code from your fetch box to link the app and if your remote is not working you can't get to it.
Optus support may be able to assist.
see if your neighbour can let you borrow their to activate the fetchtv app.
Give this a try, haven't tested it myself. Use the fetchtv app eg on an Ipad, when ask for the activation code, it is the same code as your fetchtv activation code. Once activated, the use the remote on the Ipad.
Login to My Account dashboard>click on downward arrow against your broadband service>click fetch
You will then see your activation code.