Hit the good LFS where I had found them previously months ago. I gave one of the employees i'm more friendly with a sheet of paper clearly stating both Characidium fasciatum and Characidium ranchovii along with all the common names I had ever seen them under; Tiger Tetra, Hummingbird Tetra, Peruvian Darter Tetra, Darter Tetra, and Walking Tetra.
Last time they had them they were few and sickly and expensive, and I only ended up with three from that batch. They're Tetras and I have the stocking space, I could easily add 15-20 of them, if I can find them.