Probably going to be best served by checking out fish tanks, or maybe big glass art vases. The big kind you see in floral shops where people put pine cones or artsy balls in or something. A human head is pretty big, and this is supposed to hold it, a few inches of water above it, not to mention around it.
A foam base would be pretty easy to build, just make an outline with the bottom of the jar on top of some blue or pink foam sheeting, make a larger circle, then cut out a few. Glue em together, and cut out a section of the "inner" foam to hold the jar. You could even wire up some LEDs for the inside or outside lighting if you want.
Can't help you with the head part though.
Chris