Hi,
The best thing is if you try to write something yourself, and then post it here so that we can give you comments.
My general advice is to think of it from the point of view of the person who opens it and reads it.
Why is this person writing to me?
Why should I sponsor this? Will it be good for my company in some way? Will the public know about it in some way? How?
What exactly does this person want from me? Money? How much? When?
Best wishes, Clive