Don’t forget the dollar store, if you have those wherever you are. They may have bowls and picture frames, and if you paint the backside of the picture glass (probably plastic) with acrylic black pain, you have a cheap black mirror that looks very similar to the still surface of water in a black bowl.
@jpaq87666 put in a great topic on how to use black mirrors with a whole incantation, tips and advice and all that fun stuff too: