use any flexible plastic container with a lid (butter bowl, cottage cheese container, etc.)
cut a hole for their heads to fit through
poke little holes in the bottom in case water gets in
here it is in action
I also added a wire through the back to secure it from tipping over
cut a hole for their heads to fit through

poke little holes in the bottom in case water gets in

here it is in action

I also added a wire through the back to secure it from tipping over