07 MS waste water system parts

[RangerFarra]

Hi, new here and new to vanlife.
Purchased and drove my new to me 07 2500 170”WB MB diesel from Salt Lake City through the Rockies and some serious winter weather early this February, home to Milwaukee.
Spring is closing in and I’m ready to dewinterize- however the black water dump system apparently cracked just ahead of the black and gray water release valves.
Looking for a DIY repair. ( my son a Deisel mechanic and handy) We are having trouble finding the correct diameter pcv pipe parts to repair. Menards, nope. Camping world, nope.
Looking for recommendations to purchase sportsmobile system compatible parts.
All repair options booked out. I have spring trips and attending my sons Army basic training graduation soon.

Thanks in advance.
Ranger Karen