A good place boric acid can be found is by buying Terro from Terro and or at your local nursery store. Most nurseries sell the Ortho brand boric acid powder. Keep out of reach of children. Anyway, the idea of using boric acid is that using any kind of poison is not such a good idea really. Kill only when necessary not out of habit or because its easier.
Poisons are never the answer.
Always seek balance. The bugs are just telling you when there's an imbalance. The ant gel or store bought formula should be adjusted so that the level of boric acid that the ants get is strong enough to kill the queen, etc. All store bought items are too strong to work effectively against ants unless you modify the formula. We provide 1 oz Terro Ant Bait free with every Ant Cafe we sell to get you started.