Daryl has the right idea, contact the PR dept or similar at your local cop shop ( or your local bobby if you have one). Our local underwater search unit do training exercises every week, where something has to be "hidden" in a pond or canal, so I'm sure yours would be interested in doing a search with a purpose. If as the note suggests the model belongs to a child, even better for press coverage.
They have to train anyway so no one can claim it's a waste of resources, and lets face it, the worst thing they can do is say no !!
Aston