The OP (Original Poster) was Garabaldi, and in post #10 of this discussion, he posted a photo of the type of garter-clip shown in the modern photo posted by Icewing. In other words, I think the OP's post #10 photo is the one Icewing meant in his post with the modern garter.
I'm not charging for a service so I always reserve the right to be wrong, and do my best to be helpful.
Creskol, after a bit more research, I found a bunch of similar hardware on leather garter belts.
To be fair the only ones I saw with the double rivet back were the ones you pointed out from the corset backs.
Nice work, you know your lingerie hardware quite well.