I have a Hampton Bay 42" Gazebo Fan Light adaptable. I want to add the light kit however Home Depot does not have in stores the light kit to fit this. There was once a Gazebo II fan and light but Home Depot no longer carries that. Where can I get a light kit?

Any light kit should fit, however if you are using the fan outside you may want to get a damp-rated light kit designed for outdoor fans.

Ceiling fan lighting - Ceiling Fans N More

Apparently you didn't notice I answered your question. Your loss.