I think you can go to the craft store (i.e. Michael's or Hobby Lobby) OR possibly even Home Depot or Lowe's and buy rrrreeeaaalllly thin sheets of wood.
Here is an example:http://www.laserbits.com/images/WUS096.jpg
I think you can find some that are even thinner than that.
Anyway, you could buy one of more of these, make a template, and make several of them. The good thing about wood is you can cut it to suit your needs, paint it, cover it with something (decorative/scrapbook paper, for example), and do just about anything to embelish it (i.e. add buttons and bows to the ones you use in the baby department).
I also agree with the statment about asking a place like Walmart for THEIR clothing dividers if you want more of what you already have. I would talk to a manager, though, so as not to get a store associate in trouble. Hehe. I work at a department store and sometimes we have an ABUNDANCE of those sorts of things. They either end up in a huge box somewhere not being used or trashed.
Hope this helped!