Yes, you need to issue a formal letter along with your company logo etc, so that they can make the stamp as requested. (This is for just a safe side) . You can make the stamp in any local vendor, but it will misuse later.
So its better to go a reputed vendor with legal way,
Sender's Name
Address
Telephone Number
Email Address
Date
Recipient's Name
Address
Dear Mr./Ms. (Recipient's Full Name):
Subject: (PURPOSE OF THE LETTER)
In the first paragraph, you can introduce yourself, if the recipient does not know you. After this, mention the purpose of the letter.
In the next paragraph, give out the details i.e. the facts that support the statement you made in the first paragraph. You can end the letter with this paragraph or you can have another one, if the information you want to convey does not fit in this paragraph. Complete the letter by thanking the recipient for taking out time to read the letter.
Respectfully Yours,
(Your Signature)
(Your Name)
(Enclosures)
Thanks,