I've found a tidy, but not mint black one. It's a double clamp, inline one. Branded monster.
Another one I've found is a roox, though need to measure to confirm. It's been cut down but should be longer than 300mm. It's very tidy in the most part, depending on how much post you have out of the seat tube. Black.
I may have others, pretty sure a Thompson is lurking somewhere, possibly another.
The joys of owning a GT team RTS with the 26.8 post diameter and being indecisive with builds over time. It's currently wearing a controltech in black, matching stem and bars.
I do have a race face post in 26.8, but that was intended for my other disc converted RTS which I was going to build with matching stem, bars and modern 30mm race face cranks for a bit of a retromod.