Configuring two wireless routers with one SSID (network name) at home for free roaming - Scott Hanselman's Blog
How to build a roaming wireless network between your wireless router and TP-Link Wi-Fi Powerline Extender
Home Wifi Seamless Roaming Solution 4pc 1200mbps Gigabit Access Point Ap+ 1 Ac Load Balance Flow Controller Multiple Wan Router - Routers - AliExpress
Amazon.com: RoamWiFi 4G LTE WiFi Mobile Hotspot Router, Worldwide WiFi Portable High Speed WiFi Hotspot with US 100GB & Global 1GB Data 90Day,No SIM Card Needed,Pocket WiFi for Travel in 160+ Countries :