Or several readers have commented that baby oil accomplishes the same thing. Glycerin can be found in the baking aisle of craft supply stores in small bottles. Probably at least 2-3 teaspoons per cup of water.
Grandma...........I'm Borrrrrrred!! This looks like a great winter time boredom buster (and of course snowglobes are my favorite thing). http://www.ourbestbites.com/2011/12/how-to-make-a-homemade-snow-globe/
glue dollar store tree to lid, fill jar 1/4 of the way with fake snow and 3/4 with water. stick lid on with tree attached, voila! homemade snow globe. cheap and easy, cute christmas gifts. add ribbon or twine onto lid for added effect.