There are lot of file managers that work well in WinPE
here are just a few
- ERD Commander
Those are just a few, but there are tons..just google those names or just google winpe + file managers and you will find them. Most are just .exe and all you need to do is mount the winpe image, create a folder and place that exe in the folder and unmount it.
Then browse to it through command prompt and launch it when you are in winpe.