Below is an example for the templated envisioned as Referral letter intended to the CEO of your previous working place.
Respected <Name, Surname>,
I am in the process of applying for a new job position and it would be great if you could provide me with a referral for the period that I worked within your organization.
All you have to do is to click on the following link [link to form] and fill in the form that is provided.
I hope that it would be okay with you if I use your name together with the referral.
Thanks a lot.
Best regards,