I'm not quite sure what you mean by "Humidity trays". For my trays I went
to a local nursery and bought a couple of the dark green/black plastic trays
that gardeners use to start seeds from.

They are about 24" long x 12" deep x 3 "tall. Place an inch or so of clean,
washed gravel and add water. I then take a piece of the plastic "egg-crate"
white, plastic fluorescent light cover, that I buy at the local hardware
store. Cut it to fit inside the green trays and place my plants on top of
those.

I don't know if your looking for something fancier than that. But mine work
great for me.

Hope this helps,

Francis Marion