All the reviews of the Classic HPX in Silver were from the 2011-2012 era. Unless you luck into true "New Old Stock" or NOS it will most likely be older. There is an older "Classic Lapize" model, but it is the type with a small hose. From experience that is a less than ideal situation, but some may like it.

I would go for the new black model. I know Rivendell has them.

This website may have older versions and possibly even some old Silcas, but not cheap. Call or email them first as they get stuff from many sources.. https://www.yellowjersey.org/hpx.html.

Zefals come in 4 sixes. If you get a size, get the largest one that will fit so it is compressed more and under more spring pressure and therefore more secure over bumps and road vibrations.
#1 - I could not find info on this one.
#2 - 40cm - 46cm (15.75" - 18.1")
#3 - 46cm - 51cm (18.1" - 20"
#4 - 51cm - 56cm (20" - 22")

Remember this is from the surface of the frame tubes (seat/head tubes or top/down tubes) where the pump contacts.