How would one make custom video game cases?

So recently I got my hands on a copy of the Metal Gear Solid: The Essentials Collection which includes Metal Gear Solid 1, which was for the original Playstation, and 2 and 3, which are for Playstation 2.

To my surprise, instead of putting Metal Gear Solid 1 into a regular Playstation case, they had a new case of Playstation 2 case size.

Visual: http://www.pwned.com/gamecovers/playstation2/80d6df3b67aad5cfa53e7bebb9dc188a-Metal_Gear_Solid__The_Essential_Collection.jpg

Now I know I can do this by myself, but does anyone know where I can find any templates, tips, or whatnot on how to do this?

Playstation 2 games/cases as well. I bought several used games that lacked their cases.

And just so it’s clear, I’m doing this for personal use. No intentions of reselling.