As some FF friends know, I use fleece fabric for substrate.
It soft, holds a ton of moisture, and is re-usable.
It is put through the washer and dryer, changed 3 times/week. It takes ,literally, 1 minute to change.
Obviously not good for a frog that needs to burrow.

Maybe my idea is not so far fetched ?

Check out this exo terra product. I wonder if this can be machine washed?
Exo Terra : Moss Mat / Terrarium Substrate

Lynn