I dinked around with several heated water devices for a couple years,
then settled on this, which has worked well for 10 years.
Not sure it would work in your coop tho, due to lack of space.
There are many options for each of these items.
Here's some tips about general heights:
https://www.backyardchickens.com/articles/coop-stack-up-how-high-stuff-works-well.73427/
I have used 2x4's for 12 years, they work fine.
Doesn't mean other options will not work too.
They are bare wood, with...