I purchased a TL-PA17 Kit 1 -Port Gigabit Powere Line starter kit Data transfer speed up to 1000mbps for HD/3D/4k.  I am trying to source an additional one or two adapters but I cannot find them on Amazon etc.  What can I purchase to go with my kit to make the signal much better through my old house.  Do I have to start all over again and buy something different.  I like them as they are unobtrusive.  Please help if you can.  Thanks