A “corporate kit” generally consists of a notebook for keeping corporate minutes and records, a supply of blank stock certificates, and a corporate seal. Many office supply stores and rubber stamp companies sell corporate kits as a convenient way to keep corporate records in proper order. However, a corporate kit is not required, and many people get along fine without them by using an essential file for corporate records and a few blank stock certificates if needed.
Corporate seals, similar to notary stamps but with the corporate name on them, are not required either, and I have experience that they are seldom used nowadays. Corporate kits may be handy or attractive, but if you are trying to save money, you can easily get by without them. If you decide you need or want one, the link will provide a list of companies that sell them. Most corporate kits will cost in the range of $50 to $150.