Here is a simple template you can use to write a letter of authorization to quote.
Subject: Letter of Authorization to Quote
To Whomsoever It May Concern
We/I, (You or Your Company’s Name) hereby authorize (Authorized Name) to represent us in the upcoming event. (Authorized Name) is entitled to cover all the information and details which is required for the quote.
If you have any concerns, you can ask the authorized person in my absence.
Thank you for your co-operation.