I was in Walmart today looking for Shake Weights (didn't find them). But, I found a possible cheapo version of Fitstix.
In the toy section they are selling $2 Monster Bubble Sticks (9 fluid ounces) and $1 baton bubble sticks (3.9 fluid ounces). I considered buying them, having my kids do the bubbles, and then filling them with .... something. I guess you could do water, sand, whatever since it is a screw-on top - the top contains a wand, but it looked pretty easy to break off. They look to be about the same size as Fitstix, with the same phallic shape.
I haven't tried it, but I might. At the very least, my kids get bubbles and I'm only out a couple bucks. Plus they come in all sorts of pretty colors