Hey, I'm sorry, I had a brain-mess-up moment, I guess I thought Handhelds as in not necessarily Handheld PCs that usually run Windows CE.
Otherwise, you could use Neko Project II to run PC-98
https://www.yui.ne.jp/np2/
Or PocketDOS
http://www.pocketdos.com/
But I don't know of any native operating system akin to Linux/Unix that's actually DOS. I don't think that's possible unless you just run it as an emulated program