The Kenyan Department of Immigration official web site publishes guidelines concerning visas for Kenya, including lists of those countries that do need a visa, those that do not, and those that require a referral visa, as well as how to apply. A PDF file of the application form may also be downloaded:

Kenyan Department of Immigration web site

Delegates should be aware that obtaining certain visas, notably referral visas, may take up to six weeks. We therefore strongly advise you to make the necessary inquiries and application well in advance of the meetings.

If you require an official invitation from the Kenyan Authorities in order to obtain the appropriate visa, please download and fill in the following form (MS Word format) and send it to BOTH of the following addresses:

1) weightskenya@gmail.com
2) Mr. Njiru at the Weights and Measures Office, Kenya: