I really liked the design created by Kandyhouse found here: https://www.thingiverse.com/thing:3789066.
Unfortunately I used a different brand of sleeves and the holder didn't work for me since my sleeves were a little wider and thicker. So, I modified Kandyhouse's design to fit Mayday premium sleeves. I added a 4th slot for cards due to Maydays sleeves being thicker and needing the space.
When printing make sure you print one labeled left and one labeled right. They each have one wall thinner then the rest so the top will still fit. You may need to file the slits on the bottom of the top piece to get it to fit properly onto the bottom pieces.
3D Solutech PLA