I just started with 3D printing, so this is my very first design. Luckily I already had some experience with Blender, so I used this to create the XBOX Controller and Battery Holder.
I did it in two separate pieces, because I wasnt 100% sure of the measurements. So you need some glue. As you can see on the pictures it will fit nice. Battery holder is a loose fit, but the batteries wont fall out. I made the holder 1 cm shorter than the batteries so it would be easy to take them out of the holder.
I included the blend-file so you can make modifications if you want to changes (make a thight fit, make it one piece, …)