External antenna for 3G modem

My Huawei E169 USB Modem is having difficulty getting a good signal on the Optus network at my office desk in Canberra. Virgin, who resell the Optus service, did warn this might be a problem. The E169 has a CRC9 connector for an external antenna. Antennashop.com.au sell a couple of different antennas to suit. One is a high gain wall mounted directional antenna, obviously far more than I need. There is a smaller omni-directional antenna designed to clip onto a laptop screen, which should do. But even that may be more than needed.

I noticed that the antenna socket is on the top side of the modem, when it is placed in the Huawei D100 3G Router. So all that should really be needed is an antenna connected directly to a plug, with no cable. Plugging the antenna in would then form a whip antenna on top of the router. Anyone know of such a device?