I am a big advocate of DIY. I find the obscene pricing for things like water dishes to be offensive. For what you spend on one small water dish, you could make three that have five times the volume!
I have been playing around with 4mm Plexiglas and a heat gun lately...you can make some amazing water dishes that way!
I also make them out of white floral foam, covered with a layering of acrylic media concrete (sometimes called tapecrete). You just carve the foam to look however you want, brush on a few coats of the acrylic concrete, and let it cure a week or two in the sun. Paint it as you like, then give it a few coats of clear urethane. Let it dry another week, and then it is ready for critter use!
Turns out these calcium dishes are made with land crabs and tortoises in mind. I would not use them with amphibians, myself.