I'd love to have a M4P, too. The points which carry me away from the M3 are: no 35mm frame, most are double stroke, film loading and the age (fear to loose the finder due to detaching parts) and somehow the film-rewinding.
However, the VF of the M3 could be the better one.
So I'd rather go for the M4P. Right now I'm hunting some, too. Maybe I'll be lucky in the near future. Cross you fingers for me. 😉