For my recently-acquired ET&WNC spike (recovered from just before milepost 13 between Valley Forge and the covered Deck Bridge near Hampton), I bought this framed tile thing at Hobby Lobby yesterday.
Today, I had to get a carbide bit to drill through it, and I then used steel wire to wire it in place.
I them made my own label for it and printed it on photo paper.
Here it is in place: