Amazon had (has?) the TP-Link Wi-Fi range extender N300 on sale for $16.99. It has a passthrough AC plug and it's working great.
When you first boot it up, it has it's own SSID. Bind to it and go to a URL and you can configure it for your network. Put in your credentials, hit save and you're all set.
I'm on 2 floors with 2 walls between me and my AP, but have the extender line-of-site between the AP and me and I'm getting a great signal.
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