Here's a link for some detail on a ritual for Bast/Bastet. It has some alter and offering suggestions along with an invocation to do for the ritual.
If you don't feel like using the invocation given and can't find any other, what you can do is write your own invocation to her. Or you cab just wing it. Let it come naturally when you invoke her.
"The Egyptian cat-headed goddess, Bastet was strictly a solar deity until the arrival of Greek influence on Egyptian society, when she became a lunar goddess due to the Greeks associating her with their Artemis. Dating from the 2nd Dynasty (roughly 2890-2686 BCE), Bastet was originally portrayed as either a wild desert cat or as a lioness, and only became associated with the domesticated feline around 1000 BCE. She was commonly paired with Sakhmet, the lion-headed goddess of Memphis, Wadjet, and Hathor. Bastet was the "Daughter of Ra", a designation that placed her in the same ranks as such goddesses as Maat and Tefnut. Additionally, Bastet was one of the "Eyes of Ra", the title of an "avenger" god who is sent out specifically to lay waste to the enemies of Egypt and her gods.
The cult of Bastet was centered in Bubastis (located in the delta region, near modern- day Zagazig) from at least the 4th Dynasty. In the Late Period Bubastis was the capital of Egypt for a dynasty, and a few kings took her name into their royal titles. Bubastis was made famous by the traveler Herodotus in the 4th century BCE, when he described in his annals one of the festivals that takes place in honor of Bastet. Excavations in the ruins of Tell-Basta (the former Bubastis) have yielded many discoveries, including a graveyard with mummified holy cats.
Because the Greeks equated Bastet with Diana and Artemis and Horus with Apollo, Bastet became adopted into the Osiris-Isis myth as their daughter (this association, however, was never made previous to the arrival of Hellenistic influence on Egypt). She is stated to be the mother of the lion-headed god Mihos (who was also worshipped in Bubastis, along with Thoth). She is depicted most commonly as a woman with the head of a domesticated or wild cat or lion, or as a cat itself."
"Bastet was the goddess of fire, cats, of the home and pregnant women. According to one myth, she was the personification of the soul of Isis. She was also called the "Lady of the East". As such, her counterpart as "Lady of the West" was Sekhmet.
Bastet seemed to have two sides to her personality, docile and aggressive. Her docile and gentle side was displayed in her duties as a protector of the home, and pregnant women. Her aggressive and vicious nature was exposed in the accounts of battles in which the pharaoh was said to have slaughtered the enemy as Bastet slaughtered her victims."