Wifi booster

Where can I buy wifi extender or booster? Ones that goes into your modem and a further plug in socket in bedroom?

Google

Or you could try the wee computer shop near Gama in Dona Peoa, they have quite a wide range of wifi boosters.

Mediamarkt in Zenia Boulevard...
https://tiendas.mediamarkt.es/p/adaptador-plc-tp-link-av500-powerline-wi-fi-500mbps-homeplug-av-y-2-puertos-ethernet-1200769

Pete.

all for your replies.

A word of advice.... when you set-up your Wi-Fi on the device that plugs into the mains socket in the bedroom, give it EXACTLY the same name (SSID) and password as your router (the SSID and password are case sensitive, so it needs to be identical). That way, devices will 'roam' seamlessly between your router and the extender, depending on which signal is the strongest.
If you have a different SSID and/or password then you'll need to set-up all of your existing devices to be able to connect to the extender and roaming can be less effective - depending on the type of devices you're using.

Pete.

The computer shop in Quesada behind the Sabadell bank. Very helpful guys.

Further advice - network plugs will be very intermittent when plugged in to an extension lead. Best to have them plugged in to a mains socket on their own (not always possible in this part of the world) Good luck.