I love r0adkll's designs for other handheld consoles, but no such design existed for the Game Boy Pocket.  I decided I would try to create one by modifying one of his existing designs.  

I started with his case design for the ModRetro Chromatic, mostly because of the outline of the Chromatic being similar. I did end up having to modify all the parts except for the bottom shell, to be able to fit the GBP snugly so that it doesn't rattle around in the case.  I also retained the design of being able to fit 2 games below the GBP for storage.  

I redesigned the lid to have the Game Boy Pocket logo.  

I recommend printing the insert parts from TPU, and the external shell parts from PLA.  

Here are the instructions r0adkll included with his original design, I'd recommend sticking with them:

My Print Settings:

Lid Insert

• 10% Gyroid Infill
• 3 Bottom Layers
• 0 Top Layers

Body Insert

• 10% Gyroid Infill
• 3 Bottom Layers
• 5 Top Layers

Assembly

1. Connect the Lid to the Case using 2 x 30mm M3 socket head bolts. The body is modeled to be self threading so you will meet a little resistance when inserting
2. Insert the TPU case insert into the body, the fit should be Just Right and slide in
3. Super glue the Lid insert into the the Case Lid. (I use Starbond Medium CA Glue for this, but any should do)
4. Super glue the 4 8x3mm Magnets into the case and lid. PLEASE BE SURE TO DOUBLE CHECK MAGNET POLARITY!!!!