This list is very useful; Vile isn’t quite Vi, but it’s close enough, and it includes a Windows32 binary which works with CP-1252 [1] (albeit in a separate window), and fits in under 700k (7-zip compressed).
What I wish existed was a fork of Busybox Vi which fully supports UTF-8. I’ve looked at the code and it would require a considerable rewrite to make it UTF-8 compatible, so I can see why it hasn’t been done.