Try this link for LJ Panels:

http://ljpanels.co.uk/test/index.php...6McJro1vFJ8XdQ

They list extractor ducts for the ASW-19, but the Facebook link that didn't work for you had a picture of the oval Pegase version. I don't know whether it ever made it into production, but since at least one was made, I am sure more could be 3D printed.

You might want to check out the Centrair Pegase Facebook page. It is a decent replacement for the old fly4pegasus Yahoo users group.

BTW, the link worked for me just a few minutes ago.