I found a very built-in and easy way to prompt a system-specific nice open file dialog:
import Tkinter
from tkFileDialog import askopenfilename
tk_root = Tki
There is a C library designed to perform this function, which could be wrapped in python.
https://github.com/mlabbe/nativefiledialog
Not sure what limitations the py2exe format imposes but I think this could be packaged into a pip wheel for example.
If you're developing a pygame app, there's a project called Pygame Utilities which has cross-platform support for file dialogs, among many other things. It appears to be fairly lightweight.
Doesn't look to be very well documented, though. If you download the package, run the setup.py
file in the docs directory to generate the documentation.