I believe Betsey Bay kayaks use the same size and it's not a special order, check the size with them. Theirs are made by Brooks. Or the Seals route or Snapdragon.

On the other side of this, I have come to really like neo spray skirts with the nylon tunnel and the large Velcro flap for tightening. I find them so easy to put on and you sacrifice no water leakage as well.Neoprene shrinks and many times I had to slice my tunnel and add material. Yes, I know what you're thinking. I have been wearing the same pants size for most of my life. The skin on neoprene shrinks and you'll notice the cockpit area gets tighter too.

Nothing wrong with an all nylon either. I was a rollaholic and wanted that absolute waterproof fit but for casual use a nylon is fine. You do want it tight enough on the cockpit so it doesn't sag and leak through the fabric on you. I had one of those too and just coated it with a sealant and that worked fine.