The character mods come in the form of ZIP archives. The best place to get them from, in my opinion, is UpperVolta (in the "TEATIME,FULLTIMEうぷろだ" section).
Download the ones which you want, referring to the table below.
If you're unable to download from UpperVolta, please download the torrent linked to on the previous page instead of downloading from UpperVolta.
Although you can see a little preview image (the same as shown on the previous page) of most modded characters by clicking their versions below, there are some which you can't see, due to there being more than 1 actual 'version' included in that version. To avoid confusion, you will always get a little preview image of your exact chosen version of character mod when you get to p2 of the custom guide.