This may sound a bit unorthodox but consider contacting you local Municipality, or a Municipality that has creeks with foot bridges over them. You know, the Boy Scouts at the Council 'level' may be of assistance too. And lastly, there's the Parks and Recreation Department at the County, State, and Federal levels.
Other than that, I haven't much to offer. You're going about this the right way in my mind, especially if you want your bridge to 'survive' your lifetime. Good luck with it. It sounds like a great project.