Wow that's a massive difference between the wifi and ethernet connection,
The kit you mention are called powerline adapters (in the UK) and are a great bit of kit plug one in next to your router then it injects the internet into the ring mains and you can pull either another wifi hotspot or ethernet port anywhere you plug an addition powerline adapter in.
Standard ones are fairly cheap these days but i'd look at the passthrough option if your short of plugs and keep an eye on its advertised through put for mbs as they can go from 200-1300+mbs.
I've been using them for a couple of years and are great for the smart Tv's for streaming, games consoles where high speeds and low pings are king!
Hope you get it sorted 👍