Happy Birthday!

Youtube doesn't really have any great isochronic tones. They're out there, but it is impossible to tell what frequency they broadcast in, or the ones that do tell you aren't that good. I would recommend downloading Audacity (free) and Switch sound file converter (also free), and following this tutorial. See youtube for how to incorporate your own music. Overall, the learning curve is about 10 minutes, tops. Once you master Audacity, you can create your own tones in a great variety of frequencies, and even customize them by adding in the kinds of music you like.