Shock, most fly shops that sell C&F boxes will have replacements for those boxes. Or you can order online
http://www.google.com/products?q=C%26F+foam+insert&hl=en&aq=f
Lots of different sizes available for your customizing needs. I cut out the strips with scissors, so you can put them end to end and make extra long rows, and the freedom to space them as you see fit. Nice to have some midge foam, medium foam, and some streamer foam, etc. as well.
Note, the replacement foam has a sticky back, and it sticks fine, at first. But with time the edges start lifting. Best to throw a touch of super glue, or Goop, or whatever you want, under the edges to start, and anywhere else it starts to lift or shift on you. I used Goop cause it seemed to me it'd be easier to scrape off than super glue, should I ever want to change the configuration.
I used to do this even before the Richardson. Always loved C&F's slit foam, but never wanted to spend so much money on a fly box, and didn't really care about the waterproof aspects or the threaders, just liked the foam. Solution: Buy $5 plastic fly box, rip out foam, replace with $10 C&F foam. Presto, a $15 C&F style box.