Looking for Marine Plywood source

[Mr. Sandman]

In my case I am replacing an interior latter with some (larger) custom steps I am making that will allow better/safer access to below and added (spare tackle) storage as the steps will lift up. I am building a mock up in scrap now before I cut "the good stuff". I want teak and holly faced because it will match the rest of the flooring. The mahogany will be for the rise and sides of the steps and a shelf behind the steps and match the rest of the interior trim.