Terminology is a problem here. For most "repeater" means wireless, but what you also are saying is you want to use an Ethernet LAN connection.
So to be as clear as possible, if you want a second router hanging of your primary router connected by a cable on the same IP segment and want the primary device to server up your DHCP, then you want a Dumb AP.
https://forum.openwrt.org/viewtopic.php?id=58313
https://wiki.openwrt.org/doc/recipes/dumbap
It's basically disabling the DHCP on the AP.
If you want a device that is connected on a different IP segment then most devices should be able to do this out of the box. Just connect the primary routers LAN to the secondary devices WAN.
Any OpenWrt device should meet your needs. Its configuration.
Not a dual band device, but all the ports you may want, external antenna and comes with OpenWrt installed.
http://www.gl-inet.com/product/gl-ar150 … a-version/
There is a POE version if your primary router will support that, otherwise a basic AC-5V charger will do.