Holy crap! I didn't read the whole thing, but how many hours does this guy have in this thing? The construction quality is phenomenal.
I see he cut the end caps with a CNC laser. He must have had free access to that
Just the stainless steel plate would cost a fair amount, and then to have it laser cut would be hundreds of dollars.
Man, it must weight alot.
PVC would be an option, but I don't know how you would make it look shiny like that. I suppose you could do a flat black version and just paint it.
If you have a cool scrap yard around where you are, where they will let you poke around in the piles, you may find some scraps that would work for the end caps and other parts. Machine shops and manufaturers often discard heaps of matching punchouts and such. You might get lucky and find somthing cool and unique.
Copper tube, the type that is used for water pipe, comes to mind fo the rings around the ends.
If you build one, be sure to post and show it off!