Antenna adapter cables for that device are available from all amplifier / antenna dealers out there . the connector is based on the dealer and what his antennas/amplifiers use.
i.e Wilson dealers have cables with FME connectors / Cyfre dealers have TNC connectors on their cables and Digital Antenna dealers have mini UHF connectors on their cables . The connector that goes in the USB card is the same with all dealers. You need to check out Millenicom.
The unlimited plan is on the Sprint network and it gives you 50 GB per month , with no long term contract or taxes.