If you want to target alpha oscillations, fNIRS is not sufficient, it measures oxygenation changes in the blood, which is a delayed metabolic response to brain activity, changing on the scale of seconds. EEG oscillations instead reflect real-time neuronal electrical activity, changing on the scale of tens of milliseconds. On the plus side, you can also sew EEG into headbands, there are a lot of wearable devices under development.