The best replacement for powerline adapter is repeater.

The best alternatives to powerline adapter are rated as following:
★★★★★  repeater
★★★★★  wireless bridge
★★★★★  range extender
★★★★  wireless router
★★★  wifi extender
★★  wifi repeater
★★  wireless extender

Your alternative for powerline adapter is not listed? Suggest!
Speaking about powerline adapter, one probably shouldn't forget about ethernet switch.

Other search terms related to powerline adapter and their ratings are:
★★★★★ ethernet switch
You have in mind a companion for powerline adapter and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of powerline adapter in all years. Click on graph for more.
powerline adapter
repeater
wireless bridge