All that I can tell you is that the file name is HPC2K-SDK_JPN.exe and it is a little over 51MB. Try searching for the file name on Japanese lanaguage search engines.
I had a quick look, I couldn't find it anywhere obvious and it is not something that I have archived myself, I only keep English language updates. If any member here has it, please let me know and if you send it over to me, I will make it available in H/PC:Update for the community.