Andy.
for 2.3 GHz portable I use the WIMO /SHF antennas 40 element Yagi.
https://www.wimo.com/en/antennas/vhf-uhf-shf-antennas/stationary-directional-antennas-yagi-x-quad/shf-1340
They make longer ones, but I prefer one that will fit in the car complete.

I also have a shorter antenna from Antennas-Amplifiers which was purchased just for mountain topping
https://www.antennas-amplifiers.com/13cm-antenna
OK, but designed for vertical polarisation, so you would have to change the mounting.

Stuart - G1ZAR