I'm glad I registered to this community. I also had concerns about moisture in thw Sylphyo, read this thread and ordered these medical compresses from A. for a few €. They doe not lint and leave no fibers and hold back a good amount of moisture up to 1 hour of playing at usual room temperature.
I cut one "sheet" to 7,5 x 5 cm, made a roll, put it in the mouthpiece so that about 3 cm go into the moutpiece an 2 cm go into the Sylphyos housing. So cheap that you can change it as often as needed,