For anyone else that comes along and is on Mac like I am. I ended up purchasing bmGlyph off the Mac App store http://bmglyph.com/. It is pay only, cost $10. You can use their "publish" option to set to appgamekit. It's slightly weird because it creates files named like this.
That doesn't work, but it is just because the foo.fnt file is not named correctly for AGK. Rename it to "foo subimages.txt" and it works perfectly. I contacted the dev and they weren't aware that was an issue so they are planning to get it fixed for a future update. As far as I can tell this is the ONLY option that works on Mac. If you have others please share.
foo subimages.txt
foo.png