I've been thinking, what about Band-Aids? They come in different sizes, shapes, and colors, and have a leather look to them. Granted the regular ones have holes in them, but they could be filled in somehow (or left open for a sporty look). The parts with the foam could act like cushions or help accentuate the seat. Of course, I haven't tried this and don't know how effective they would be (especially with extra glue). It just seems like a material that is thin enough for 1/24 & 1/25 scale, but still has a leather look. If someone were to try this, I guess Band-Aid brand would be the best.