The Pentaclip is a Brompton product*, you can order a new Brompton with a B17.

As a large manufacturer they have suppliers that ship
their component parts, contract ordered in bulk.

I got the last X series upgrade Brompton offered, a few years back,
Vitesse with a different Rail bend batch, sourced from Fizik in Italy.

* best saddle clip for plain seat-posts, $30 on its own,