McMaster-Carr is my favorite source for t-slot extrusions, they carry everything visible in that picture;
https://www.mcmaster.com/structural-framing/t-slotted-framing-rails/
In Western MA, McMaster can get stuff to you overnight with "standard" shipping depending on when you get your order in.
8020.net is another good source a lot of 8020 fabricators like.
FWIW, I am modding an old enlarger to be my copy stand, but there are many pathways to the "ideal" solution. Fabricating something out of 8020 would probably be my first choice if I didn't already have a suitable enlarger sitting around.