Magnus' link is to a GUI program that works with FFMPEG, apparently you can use FFMPEG to encode to ProRes422HQ:
I'm on a mac so haven't tested it myself.
In command line use -pix_fmt yuv422p10 or -profile hq instead of -pix_fmt yuv444p10.
I.e. the command line should look something like this:
ffmbc -i <SourceFileName> -vcodec prores -pix_fmt yuv422p10 -acodec copy <OutputFileName>.mov
DISCLAIMER:Although the resulting file is in ProRes, I was able to get a decent transcoding to ProRes with neither FFmbc nor FFmpeg so far (i.e. to get the same quality as with encoding to other 4:2:2 and 4:4:4 production codecs accordingly via After Effects or Adobe Media Encoder)
There is, but it's expensive and you won't like it. Buying a Mac would solve your ProRes export problem. It's probably the simplest solution, and it's the best solution from several points of view.
Here's a free Windows program -- no guarantee of suitability or stability:
If I find other software solutions, I'll edit the post.
Here's a plug-in for After Effects, but it doesn't look simple:
And another free program -- same caveats: