as I had the same issue here in Italy and being on 220V, the power adapter can’t be directly connected to the power line. My first thought was to get a 220V -> 24Vac adapter providing at least 1000mA, but that ended up in finding mostly adapters with a UK plug
So another solution would have been to purchase a step-down converter to half the 220V to 110V and create a sort of “adapter sandwich”: one on top of the other. But I didn’t like the idea of the need of 2 trasformators and having 2 points of failure.
I did solve with purchasing a DIN rail mounted trasformator converting 220V to 24Vac and 24VA as output (1000mA) http://www.conrad.it/ce/it/product/515213/Comatec-TRAFO-24-VA-24V-Alimentatore-per-guida-DIN-24-VAC-1-A?ref=searchDetail. As next to the enclosure I have a small electrical cabinet with different circuit breakers, I can mount that device in it and supply the power to the Rachio 3
24VAC is what some smart door bell systems use e.g Ring Pro. So consider looking at a local bell transformer.
…and pay attention to the max output current. Rachio 3 requires 1000mA