This thread discusses the system and has nice parts diagrams in posts #1 and #5. Which exact parts are you needing?
https://xoutpost.com/bmw-sav-forums/...ow-w-pics.html
I replaced a lot of the vacuum hoses, perhaps including the ones you need, on my 2001 3.0i when I had it all apart this summer. I used this stuff, which is really nice. I'll buy more of it next time I get stuff from RMEuropean:
https://www.rmeuropean.com/Products/...FG21-V592.aspx
^^ that's the pretty small stuff. I agree that if you've got the plastic fittings, pretty much any rubber hose would work. Vacuum hose by the foot, of the correct diameter, from your favorite local auto parts store should do it.