Simply replace the unfilled areas such as "" and "[date]" with your information.
Dear [Customer Contact],
As the [position] of [vendor company], I want to personally thank you for your business. I know that you have many choices during vendor selection and I am pleased that you have chosen our company. I expect this to be the beginning of a fruitful business alliance.
I would like to extend to you an invitation to tour our facility. I would like to show you, first hand, our company's commitment to excellence. You will have full access to all of our production processes. I am confident that you will leave here feeling completely assured that your products are being made using the latest technology and with the strictest quality standards.
Please let me know when I can schedule your tour.