For good inks, hit a proper artist supply store, not a craft store like Michael's. There are several ranges of artist's acrylic inks out there. I think most of mine are from Windsor & Newton - but they're buried in a box somewhere at present, so I can't tell you for sure...
GW & Reaper also do ink in their hobby paint lines. GW's are very nice; I imagine Reaper's are too, as their paints are excellent. Reaper's are (surprise, surprise...) cheaper than GW's...