Another source would be
Frost Hardwood Lumber Company | Quality Wood and Related Products for the Woodworking Industry in
San Diego. Although if you can locate, & get in touch with a few boatbuilders in your area, or otherwise, odds are they'll give you such a piece for free, or at most a 6-pack. And a lot of the lumber distributors mentioned might be kind enough to give you some POC's.
Also, try both the Wooden Boat
Forums, as well as the periodical of the same name (especially the classifieds section in the back).
If you're not 100% set on teak, take a look at Sapelle & Meranti, including/especially in
Marine Ply form. They're gorgeous woods, often enough used both for
hull construction, as well as
interior joinery. And... a decent percentage of
Marine Lumber distributors will give you sample pieces of about the size which you're looking for, for free.
- Well, kind of free. Perhaps a better term is, to be used as stock in order you to compare them for use on other, & or larger projects. Kind of like you can get small pieces of tile to take home from a place which sells home remodeling materials.
Also, try; dumpsters @
boatyards &
marinas,
posting "wanted" notices (online & on bulletin boards)... you'll find some
cheap, or gratis, long prior to running out of ideas & resources.
PS: Wisdom would suggest that you post that you've found what you're after, when you find it, or you may be deluged (almost akin to The Great Flood) with responses.