This should probably actually go in the questions section. Or better yet, contact the artist and get permission instead of asking here. But basically I found a source for male genital models, with relatively minor adjustments needed to convert to all-quad. I've done the conversion on one mesh already, and it loads in MH and looks great, I just don't have permission from the artist. If you want the .mhclo or the .blend, message me.
Source (warning: very NSFW. Both the page and the entire site. )
edit: actually, no wait, forget the part where I said it looks great... when I apply it to existing characters, the shape gets disturbingly squashed and I have no idea why...