Poly 318 heater hose fitting

Check to see if any of your local auto parts (Here it's CarQuest) carry the Four Seasons line .It's a Heat and A/C parts. I that's where I got my pipe nipples for my Poly 318. I'm suprised that Ace didn't have what you wanted. The local here has bins full of pipe nipples with 1/2, 5/8, 3/4, 1'' with hose barb end.