I have tried the already listed cheap Ikea Trådfri Zigbee outlets, which work great.
Also tried Nexa ZV-9101 Z-wave plus dimmer module with a momentary switch and the Z-wave "Generic Z-Wave Dimmer" driver, working great.
Tried the Nexa AN-179 Z-wave plus switch module with a standard switch and the Z-wave "Generic Z-Wave Switch" driver, working great.
Might change the switch to a momentary though, as it has to be double flipped when used physically after being remote controlled to its reverse position.
Also, you can report new devices that work properly with the built-in generic drivers to @mike.maxwell from Hubitat. He can then add the 'fingerprint' of these devices to the generic drivers so that they will be auto-assigned a driver when they are paired with the HE hub.