Wouldn't brass rod, the correct diameter, cut to an appropriate length, do the job? More expensive than nails, but I suppose cheaper than track pins.
After all, most of my GG/Ross/Curtis track is joined with brass pins. Flat in this case, but still a track pin. I do have some GG pins that have a "steel" color, but I have never given it much thought. For all I know they are plated brass, for some reason.
Anyway - brass, the go-to metal, and easy to work with. I have not priced brass with this in mind.
