Tioga post happened to show up on ebay just a couple days after I brought the bike home.
If it's not the original style post, it is, at least, very similar. Interesting to me is that it appears to be anodized? I don't know that I've really seen steel with an anodized finish before. Or, at least, I didn't know it when I did see it. Anyway, will probably get a powdercoat instead, as I have that option readily available ......
Not holding my breath on the rivet GT saddle. May end up with one of the modern retro-style rivet's that are all over the place .....