This is a modern list of items, with a base number of 100, as well as some alternatives, that could be found by players looting or investigating a pet shop, excluding live pets themselves.
Whether or not any of the items are any use will depend on the creativity of the players. Some definitely have potential uses, other than their original ones; others, not so much. The list is weighted towards cat and dog items, but there are things for other creatures, including such as wild birds.
Some example results are:
63. Heat Mat (Mains powered, a flat mat used to heat the floor of vivariums)
64. Litter Tray (For use with cat litter)
65. Live Reptile Food (Live food for feeding to reptiles, in boxes, such as crickets, locusts, hoppers, fruit flies, mealworms, morioworms and waxworms)