the best thing ive ever seen for a bowl that wasnt an actual bowl were these things you put on a bottle of frosting, so that it comes out in fancy shapes. no idea on the cost, but i bet any store associated with baking would carry them. theyre basically these little metal cones, perfect size and shape. and the holes are usually a cool shape too

dont use clay, unless its a special type that says can be exposed to a flame. most clay has some bad stuff in it that would be released if it got hot enough.

or you could abandon that idea, find a nice lamp at a yard sale or something and make a hookah, if you get the right kind ittl evenj come with a big metal tube that the wire runs thru, jsut get the wire out and all you need is a bowl and hoses. im currently doing that now, with this fuckin beautiful ceramic lamp.

good luck!
peace