What's the best alternative? I don't think you can use the ProRes codec on Windows machines.
Prores is available in some profiles via libav, ffmpeg, fmbc but more importantly what does your NLE or grading app except?
http://hdcinematics.com/tools/AWProClient.html
This converts to ProRes. You could also use CineForm or DNxHD.
You can try something called anothergui. Also converts to prores