Well, here is pretty good way to fix that on the cheap.
It should last longer than any replacement insole you could come up with and be more comfortable than the original.
Note: Because this is a thicker material, you'll have to replace the insole in both shoes, the broken one and the matching shoe as well so your feet will be at the same height when you are walking around.
Step 1: Things you need
shoes that need a better insole
pair of good scissors