Linksys via eBay offers the refurbished Linksys AC1200 802.11ac Amplify WiFi Dual-Band Range Extender for $29.99 with free shipping. That's $10 under our mention from last November and the lowest price we've seen. (It's $70 less than the lowest price we could find for a new one.) It simultaneously extends ranges for 2.4GHz and 5GHz bands and features Ethernet and two external antennas.
No warranty information is provided.