It shouldn't be necessary to create a new transaction for the material master. You can define a new screen sequence which defines the screens and subscreens you want somebody to access and then direct specific users to specific screen sequences using configuration.
It's all done under Logistics - General --> Material Master --> Configuring the Material Master in SPRO.
I would suggest copying the one you are using now and deleting the screens you wish to hide and then make the new one the default and asigning the existing to a specific group of users. This way new users don't get the full acess without it being specifically granted.