You could go buy a foldable (and prettier) portable dog water bowl for $10-$15 or you could make one in less than 30 minutes and do some recycling too.
Step 1: Materials and Tools
Flexible Plastic Sheet at least 28cm x 28cm
Piece of scrap wood
I am using some housewrap that I got from the throwaway pile at at local construction site. It feels like fabric; is light, watertight, and strong. It is used in the same way that Tyvek is. (I do not know if Tyvek would work for this project).
And the following tools: