Pirecatam is available at bulknutrition.com
I personally liked what Spike! by Biotest did for my concentration and focus.
Obviously, a good multi-vitamin, a set sleep schedule, and a healthy diet are the no-brainer basics. Make sure you get those before adding any fancy stuff.
Fish oil, acetyl-l-carnitine, phosphatidyl choline (lecithin), and vinpocetine are also great additions