My garage is a stand-alone structure about 20m from my house and has next to no Wi-Fi coverage a.t.m., but I want to have access to my home LAN in the garage.

The garage is a very conventional structure of the "Versatile" type (but not that brand AFAIK) with a light timber frame and a galvanised steel 'weatherboard look' exterior and a long-run tin roof. There are two windows, neither particularly generously sized - it's a garage! The design makes it quite an effective Faraday Cage, with very limited penetration of any** RF.

My existing LAN features a Spark Huawei router / WAP at one end of the house and a Ubiquiti UniFi Mesh AC1200 WAP towards the other end, much nearer the garage. You can't really 'see' either WAP from inside the garage.

The garage power supply is on a separate sub-main with its own circuit breaker on the main board.
The isolation between the garage supply and the house is sufficient to make a mains power-line LAN extender not work - I have tried that. Sigh.
The garage power supply is direct buried, so there's no duct to pull / push a cable / fibre through.
I could run an aerial cable, but that would be ugly and the internal run at the house end would be really quite complicated.

I'm really looking for a wireless solution.
Can I buy something that would have an antenna outside the garage to pick up the UniFi signal and another antenna inside the garage to broadcast the Wi-Fi? I've looked on the Go Wireless web site, and realise I know just enough to be dangerous, but not enough to work out what to buy

** I can listen to RNZ on 567 MHz AM, but the same station on 101.x MHz FM is too crackly to be worth listening to.
     Wi-Fi on 2.4 or 5 GHz really doesn't want to get in from the house.