>>56>>54 here, I've zipped the MS PMincho and PGothic fonts and upped it here:
http://www.mediafire.com/?mhnytmy0iyiThose are Microsoft's Japanese fonts and although Mona should be equivalent you can try them as well. Most VIPPERs are using Windows because of its dominance of the market so these are the fonts they use.
You can get them as part of the Japanese language packs from Microsoft and they're on most XP (and I think Office too) install CDs. If you lack any of those you probably have a friend with XP who can send them to you. I'm pretty sure Microsoft doesn't like to see them distributed so I'd ask the tanasinn.info wiki administrator before linking to them.
To set them up in Firefox follow the instructions from the header at 4-ch but use the PMincho for the serif typeface and PGothic for the sans-serif.