I found the pattern at the LQS, but they still haven't gotten the ruler in stock, so I made 10 degree templates for each strip out of posterboard (and saved about $25 in the process). I thought the pattern instructions were a bit confusing for my very visual way of thinking, so I ended up referring to pictures, cutting each "strata" separately instead of stacked, and then sewing them together the way that made sense to me. I know there's a method to the instructions, but I was having a hard time following it, and will re-write them for my own use!
It was a fun project and I'm off to the store later today to buy some "purples" for one for my DDIL!