I can personally recommend “IKEA TRÅDFRI Signal Repeater” as a dedicated Zigbee Router device.
It for example works much better as a Zigbee Router in comparison to most Zigbee power-outlet plugs.
Another powerful option is buy a few CC2652P dongles and flash with Zigbee Router firmware, see ex:
Once such CC2652P dongles is flashed with Zigbee Router firmware can use USB-changer for power.