I have been collecting the polystyrene (foam) boxes from my local Hotel (pub). They are the boxes that have the salmon delivered in. They store many of my projects, including my pens. I just add a frozen ice brick into the box and this protects the pens from the heat. Longer items would fit in there easily as well. I use bubble wrap to further protect the items.
The plus side is, they are quite strong and stack-able, and they are free.
link broken so removed.
Dave