For this I would have to research. I looked at my local leather shop for some patterns and found them very costly. Not only that, they were limited to a specific size and would take some serious modification to adjust for different sized feet. Next was a search online, where I found the resources, strangely, lacking. There were sites that offered patterns, however I ran into the same issues that plagued me at my leather supplier.
For the plans I was searching for, I had to go to the source. I planned a trip to the Canadian Museum of Civilization and decided to study many of the styles they had on display. After taking lots of pics, many of which were closer than the museum security were comfortable with, I started to read some of the descriptions. Instead of using a pattern for their mocs, natives would use the person's feet as a template, then draw the pattern directly on the leather as a way of creating a custom fit. A bit more research at the local library would confirm that and so I was able to design more of a technique than a pattern, that could be modified to fit any foot, and was based completely on traditional craft.