These would do nicely TECHTOO WiFi Antenna Dual Band 7dBi 2.4GHz/5.8GHz with RP-SMA Connector for Wireless Network Router USB Adapter PCI Card IP Camera DJI Phantom Wireless Range Extender FPV UAV Drone (Black 2-Pack) https://www.amazon.com/dp/B00O0O0E8U/ref=cm_sw_r_cp_apa_qQjkzbN90Q27N
You could try to relocate the routers so they have line-of-sight with each other to increase signal strength. Place them in a window at each house so they face each other. They do make detachable hi-gain antennas, but you would have to check if your equipment accepts this type of connection (it's a small coaxial connection). You can buy a pair of them for like $15-20.
It woks best with them. It should have come with them but if you lost them or it didn't come with them pick some up. Not recommending these particular ones, they're just the first I found so IDK how good they are. https://www.amazon.com/dp/B00O0O0E8U
I bought my antennas on Amazon and they work great.
TECHTOO WiFi Antenna Dual Band... https://www.amazon.com/dp/B00O0O0E8U?ref=ppx_pop_mob_ap_share
I've just installed these new antennas:
https://www.amazon.co.uk/gp/product/B00O0O0E8U/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
And now my PC wont connect to my 5.0ghz wifi, does anyone know why??