One antenna you may like to have a look at is the Borg Twinfire. These antennas can be used either on their own or as a feeder for a parabolic grid. When compared to a 15dbi grid antenna they were only about 2dbi down in signal and for something that is less than 1/4 the size we think they work prety well.

We will have a range of Yagi's avalible shortly.

As an alternative you could try a pair of Ingot antennas however over that distance you would need to make sure there was no movement on any of the poles as the beamwidth is prety tight on them.

A couple of grid type antennas would also work well. the 19's should give you an exceptional signal at that range.

Regards
Andrew