Hi there, and welcome to TamaTalk!
I've moved this thread over to Virtual Pets - General, as the Chickpet is not a Tamagotchi (Tamagotchi is the brand-name of Bandai's line of virtual pets, which created the product-category), but rather a competing/generic virtual pet from back in the day. The Chickpet is part of the Gyaoppi family of virtual pets.
According to
this page from Tamenagerie (which is a large virtual pets resource), the Chickpet was also released under the names of Chickenoch, Chick Duck, GAAA Hippie, and Pi-Yo Bird. These do not all use the same shell designs, however.
Searching for any of those names, or for a Gyaoppi chicken on eBay or in other places where used virtual pets are sold is what will most likely help you on your way.
EDIT: The "
Vintage Electronic Toy" section of the Japanese virtual pets-centric online store, Japan You Want,
currently has a GAAA Hippie for sale, if the pet and the colour are more important than the specific shell design.