buy an old mahogany piece of furniture and cut the strips yourself, 1 piece of mahogany furniture will probably last a lifetime of models, when making a model of a friends boat, I was gifted 2 lengths of burmese teak, - off cuts from repairs, two pieces about 3 foot long, 2" thick and 4" wide was easily enough to make all the cabin sides, transom, decking- and well, everything that needed to be made from teak, but I have also used the timber from the doors of an old wardrobe, picked up for a few pounds at a charity shop (the rest was mostly plywood and is still functioning as a cupboard) I also found a big bagof veneers at a car boot sale, that will probably keep me going for years, hull planking was done using wooden blind slats.
