I thought we were going to be without an external antenna model after the VT900 became unavailable, but they have come out with a new model.
This one should be compatible with every Australian network, though you'd probably be silly to go with anything other than Telstra anyway.
I/O: 3 digital inputs , 2 outputs and 2 analog inputs, 2 RS232
Bands:
LTE-FDD: B1/B2/B3/B4/B5/B7/B8/B28/B66
LTE-TDD: B40
WCDMA:B1/B2/B4/B5/B8
GSM: 850/900/1800/1900MHz