US source of Panzerholtz?

Briefly looked into accessing some Panzerholtz and ran into 
the same issues as the OP specifically distribution and machining.
Ended up going with some Bamboo laminated sheet material
a friend uses in his manufacturing facility and price was
right shall we say.

Not in quite in the same league as PH but this stuff is also abrasive to cutters and very dense due to the many laminated layers.

At one point I made the regrettable decision to run an edge on the jointer
and it became immediately obvious just where the layers were laminated as it left matching groves in my new blades there after only very good carbide and replace when dulled.

Picture of plinth in my system page.

Right Teo, you need diamond tooling for this. Rich, far cheaper, easier to get and deal with is solid surface material. I like quartz products best. You can go to installers and get cut offs cheap. Laminate it with a plate of aluminum in between and you'll have a wonderful plinth.  

I did a DIY plinth several years ago and settled on Corian/MDF/Corian.  The MDF was soaked with a very thin 2 part epoxy (Smith Systems Clear Penetrating Epoxy Sealer or CPES), sort of a poor man's Panzerholtz.  The results were quite impressive and very inexpensive to build.

https://www.diyaudio.com/forums/analogue-source/312473-diy-cld-plinth-design-measured-approach.html

I used panzerholz B25 for my DIY TT plinth. Agreed, hard to work with, gummy (the glue) and hard (beech veneer). I did most of the cutting with a jig-saw (German blades) and file, and a diamond hole saw. Takes a good finish.

The thing is, it's acoustically dead, and it epoxies up very nicely, which is important for constrained layer damping. Which Delrin does not (epoxy nicely).

One of the very best go to materials, IMO. Worth the price? Depends on how you value your design time.