In case you or anyone else feels like adding additional features in the future, such as reverse converting back from html to cgp, I'll still more than welcome them.-Cocoa
Something for you to test: HTML2CGP
Still in Powershell, has a simple GUI:

Extract all files to a folder somewhere and double-click the shortcut to run. You should see the normal PoSh command window open then hide and then the GUI opens.
Two buttons, self-explanatory, the
Output: line will have simple instructions, (choose file/folder), progress messages, (converting file xxx, etc), as well as show where the output went.
I've changed it so that it uses whatever the system character encoding is for the input and output, (at least I think I have, it's a bit hard to test since I'm stuck with English

).
eg. If your system is set for Simplified Chinese then it should read/write the .cgp files in that language. However, if your system is set for OEM437, (or something), and the files are Simplified Chinese characters and ANSI encoded, then you'll get something indecipherable.
That's what I got anyway, even though I'm set to OEM850 the output files were byte identical to the original input files after converting to HTML and then back to CGP, so in theory it should work.
Requires Powershell v4, should open a requester if you haven't got it (haven't got anything to test it on).