Going to Mt. Pulag is just merely for hiking, so there's not much souvenir shops nearby. In front of the office where you get to have the orientation, is a Sari-Sari Store. In this store you can only buy the following:

♔ Snacks
♔ Drinks
♔ Tent
♔ Bags
♔ Flashlight
♔ Hiking Clothes
♔ Hiking Tools

More of Mt. Pulag tips and travel guides here.