Check out
www.gardensalive.com - it has environmentally safe garden products. Here is what they have for ants:
LIQUID ANT KILLER
Just put a few drops on ant trails and in cracks and crevices. Ants eat the bait with borax and carry it back to their colony. Bye-bye ants!
There's also diatomaceous earth that you can try and
www.planetnatural.com has a liquid and killer similar to the one at Gardens Alive.