Contact the Westerly-Pawcatuck Chamber of Commerce in RI. They originally worked with a Duck company and then purchased the ducks and run it themselves. It is a huge event and they donate a certain percentage of money to the schools that sell the ducks.
There is a fundraising company that does this, but as far as I can see it would be fairly simple and cheap to do on your own. Contact your local dollar store or discounter (Wal-Mart) to see about buying a bunch of rubber ducks. I think the company is Great American Duck race or somthing real similar. They do turtles as well.
Turn it into a whole event with snacks & games, kind of a mini carnival.
Replied by <fundraiser> on topic RE: Duck Race
You need to be located near a body of water. Then you sell rubber ducks to each person for maybe $5 a person. Each duck has a number on the bottom. The first duck to the finish line wines a prize. Cute idea!
If you search "duck race fundraiser" on the internet you'll see lots of websites about it.