I get stainless steel pet bowls from the $2 shop, they cant be tipped over as there is no gap at the bottom, they are easy to clean and dont cost a lot.
i use the XL 'natural rock' looking ones, just cos i like the look of them.
....id love to see an extra large snake try and soak in one tho, or even a large or medium snake,...i'll have to get something bigger for some of the guys soon,...