The Blaster Shotgun and the Alien Blaster cannot be crafted, since they don't have a recipe.

Because these are only collected by looting...

Except you cannot? The closest thing you can get is the Blaster Rifle from the Stormtroopers and the Outcasts, and they don't even seem to spawn normally.
Unless I'm missing something else, there's no way to obtain those weapons.

Finded the missing Blaster Rifle recipe in by using NEI: You needed the harden glass from other mods to craft it (In my option, I'm using Thermal Expansion)

But sadly, I still can't finded the Alien Blaster's recipes...