A wifi router (there are some pretty small ones and some pretty cheap ones (but no decent good small ones) that you can hook up as wifi access points. (Plug a LAN connection of the router into your Ethernet network and disable its DHCP server (in software, bu connecting to it and turning off the "enable" box).
Or it's possible (I haven't looked ) that there's an Ethernet adapter that will work with the S5. (Probably about the same price as a good small router, though.)