PN is waaaay back with wipers in 17,000 part of catalog, not with engine stuff. Hard to find in good shape, and I've never run into NOS, so fleamarket time.
Mushroom part is a silencer, usually defunct because felt inside disintegrated and was incinerated by engine.
Functional repro: Get a bolt matching the main part...it is a standard bolt thread.
Put a block of wood in drill press, drill hole that is snug fit on bolt threads. Drop in bolt, secure it from rotating with a wrench, drill a hole endwise right through it. You want a cheap bolt, not anything that will fight the drilling. Drill out outer part of hole to suit a bit of tubing for the wiper hose, cross drill the shank to get vac to the little banjo fitting for distributor brake. Take it to the parts store and get a couple copper washers from their brake hardware collection.