Fizik Unisex Vitesse.. I got mine thru my Brompton dealer , the British company got the Italian one to make a production run with a particular steel rail bend

to work with the Saddle clip and plain tube type seat posts .. was Part of their Light weight Offerings in the past , discontinued , limited to what is in shop stocklist

In UK SJS Cycles has a few (I note.. Online.. but protected sales territory they wont ship to the US)

Regular rail The Vitesse CP3 is more thickly Padded, It too is discontinued..