I found these great (and safe) pretty stainless steel bowls made in the USA. They even have non-tip ones which are perfect for ferrets! However, I want to know if it's safe or not because of the rubber rim at the bottom of the bowl. But, I would also supervise my ferrets while they ate to prevent them from eating the rubber rim. But just in case, I am just wondering....I tried a link, but it doesn't work...So you'll just have to look it up, the brand name is "Platinum Pets"

I use the metal bowl with the rubber on the bottom, neither of my ferrets even paid attention to that rubber. I know my boy used to scratch at the water and make a mess by pushing it around but never tipped it and never had issues with rubber. That's just my experience though.

You can find bowls without the rubber with the same build though, if it is something to worry about.

I have this bowl that I used outside the cage. http://caseyshiddenpantry.com/spilllessbowls.html