Early in the war (1937, etc.) many of the better KMT divisions were trained and equipped by Germany, wearing German kit with puttees. Later in the war, many were US trained and equipped. But Japanese in caps might do too. At 10mm scale, most of your conversions would be with the brush. With luck, someone out there has some other ideas too. My main 10mm source is Pendraken.
Korean War North Koreans in cap might do. Irregular make 10/12mm modern bush wars figures in caps. They are armed with AK47s. If you don’t look too close…
I’m not aware of anyone making guys in baseball caps and puttees, but that would be just the thing.
If it’s not stretching your timeframe too much, the Assam-based Chinese divisions fighting in north-west Burma as part of Stilwell’s ‘X’ force from 1943-1945 were dressed in British tropical gear, so you can use British 8th Army ‘Desert’ figures (albeit with long puttees instead of socks). This also applies for some units of ‘Y’ Force in Yunan. However, many of them received US M1 helmets, which makes things slightly problematic, though there were enough of them wearing British helmets to justify the use of 8th Army figures.