Where’s the best place to buy Ubiquity?
Don't know about best, but this should do.
UISP airMAX NanoStation M5 loco - Ubiquiti Store
Low-cost and efficient broadband 5 GHz CPE.
eu.store.ui.com
and this is what to do when you get them
NanoStationM/locoM Series Quick Start Guide
dl.ubnt.com