I remember seeing these on eBay but this was around five years back. I normally empty the contents and keep the kit as a memento. I got into this phase of collecting them a while back, that is when I tried to buy a few from eBay but then decided against it as I wanted to have my own collection. They used to sell for around $15-25 per kit.
Try putting them up on there, I am sure you will get a buyer.