Crypton Vocaloid Miku Append Software
This is an unopened copy of the Vocaloid Miku Append software for Windows. It is able to be installed as a stand alone application without the other Vocaloid applications. I bought it in Tokyo back in 2017/2018 and never opened it.
It is in Japanese. I know there are unofficial translation packs people have made available, but I cannot tell you which ones might work since I have never tried them myself.
I am also not 100% sure on anything regarding compatibility. Just that it was built to run on a Windows operating system.