You will think this tip is strange but, I would recommend checking your local hardwood yards and or mill-shops for the dunnage they stack packs of lumber on. These are usually 4 x 4's by about 4ft long. and if they come from northern domestic mills the material will be mixed hardwoods...I have found beech that was near perfect for plane making. as well as other varieties of specie.
This is also a great source for bench legs.