If you can get some translations, there's some Japanese clubs/vendors in the Web links part of the menu that might have what you need. Maybe BProjects, as they raced a B310 coupe, & might be able to source one for you. They're probably still racing these cars in Japanese Historic racing, so that could be a start. Or if you're looking for a 'Wing' wing, maybe a local metal fabricator could make something out of steel or alumin(i)um. Also, check out whats available for some European cars, as I can remember people using rear spoilers intended for Golfs & Audi's on 1200's. As the cars are approximately the same size, so something could work for you.