I be always wanted to find a synthetic vellum that looked like the historic real thing but have never fond one. You know, something that looked like a non plastic organic translucent surface. If anyone knows I would love to buy some for printing text wall labels. Wish some one would make one. Hahnemuhle does have that Torchon parchment surface and it is very sharp but thick opaque cotton.It has a great coating. I use that for wal labels and portfolio text. Also I like to use the Belgian linen which is coated by jacquard and sold as the fabrisign line. Very beautiful and you can but a 42" sample roll that is about 8 feet long. I make scrolls with it as it hangs very flat.
As for inexpensive bleached and unbleachd raw kozo this place
www.mulberryandmore.com has it in rolls and sheets and it is cheap. Our local Blick art supplies carries it as well.
I printed on it for years until the sharper new coated products became available .
What I used to do is tape it to a piece of poster board to run through until someone told me to just turn off the vacuum on the printer. On the hp I never needed any backing sheet.