I used Norvuzirf's mod as a base to add even more hidden items back into the game.
-Volition (broken, doesn't show the Volition logo unfortunately)
-Mens Free Throw Jersey
-Womens Free Throw Jersey
-3Rd Street Hoodie
-Fleur De Saints Hoodie
-Crooks & Castles Jeans
They can all be found at Planet Saints.
As far as I know there's not a single mod that adds these items without changing a whole lot of other things, which is why I created this.
Also, the Matt Miller Avatar suit can also be added via this method, but I don't really see the point as it's way too glitchy.
Install the original mod from the first page, then download this customization_stores.xtbl and replace the original with it (same place as usual, the folder where you have your SaintsRowTheThird.exe).