I haven't divided tubs for snakes, but here's what I do for other dividers.
First, I buy a container of "Great Stuff", you know that expanding foam from the hardware store.
Then I use mold release (Or cooking spray if you don't work with plastics) and spray down the inside of a new, empty tub.
Next, fill the thing about 3/5 of the way with foam. Don't worry, it will expand.
When it's done growing (About the next day), use a modeler's saw (or hacksaw, coping saw, any very fine toothed saw) to cut off the top part where the foam has escaped the tub.
Next, turn the tub upside down and smack it until the foam drops out.
Cut the foam into pieces about 1/2 inch thick so that you make multiple dividers. These dividers will fit your tub exactly.
Lastly, wrap them in shrink wrap or similar so the snakes aren't exposed to the foam.
You may not want to house snakes in the tub you used for the mold, but you now have an endless supply of dividers!
Hope this helps, sure works for dividing parts in my plastics lab.
Apple2