This is a 2DS case that could get changed to a 3DS case I think it is the same width.
Alright so you will need a little more than a 50g ball of fingerling yarn, you could use a thicker yarn but you would have to adjust the pattern to work with it and the holes in the middle of the scales would be bigger. Best to use a smaller hook size like a size F that is what I used!

●●●LINKS TO PATTERN●●●
☆You can find it at my blog
☆Or on my Deviant Art