This was edited for practical concerns.  First, the Parker ST series seals on the short spigot at the nose of the plug, not the root shoulder of the plug.  Blindly mimicking the geometry of the ST plug means that you're putting a rough printed surface in forced contact with the o-ring for no reason, likely damaging it (the service o-ring) in the process.  

Second, the shoulder-mounted o-ring (the unnecessary o-ring) doesn't seal anything since it's after the locking balls, but it does weaken the part.  The hose probably should drain when you roll it up anyway.  That's how it doesn't get damaged if it freezes.  

I removed the nose portion and replaced it with a generous chamfer.  It's not quite to the OEM 120 degree spec, but it'll do.  No more dented o-rings.  I also removed the useless o-ring groove at the part shoulder.  It's just a plug to keep spiders and wasps out.  It's supposed to leak as needed.  

I would have just designed this part from scratch, but Parker's CAD files are so infuriatingly bullshit that I refused to bother.

I did all this crap in SCAD, but all you get is an STL.  It works.  I didn't take a picture because I'm drunk and I don't care.  Trust me.  Good luck.

EDIT: okay they fuggin made me take a picture.  You're welcome.  Print this POS plastic doodad and stick it in your machine's hole.  Do it.  I dare you.

EDIT: I vaguely remembered uploading something last night, but I was pretty sure it was just a dream.  Guess it wasn't. :D