Print two of the tpu_seals in (you guessed it) TPU, or any flexible filament that will provide an adequate seal. The barbed port and nut can be printed in whatever you like. I chose PETG.
Drill a 3/8" hole wherever the port will be placed, and assemble while placing one flexible washer on each side of the medium being secured to. Use a wrench to tighten until leaks are gone.
Only the barbed inlet portion should require the use of supports.
Print the seals in TPU.