Optoma's business projectors (the old EP716 and EP719, and the new EP706s and EP709s) are 4:3 in their native resolution, which is either SVGA (800x600) or XGA (1024x768). One exception to this is the EP1690 which has a 1280x768 native resolution, but I'm not sure this is locally available.
Optoma's HT projectors like the H27, HD70, HD72, HD81 etc. are native 16:9 projectors.