Trail Tech 72-A00 Silver Digital Tach/Hour Meter https://www.amazon.com/dp/B00AR2R090/ref=cm_sw_r_cp_apa_i_kD0.AbFVX1D11
This is the one I bought off of Amazon for like $20, but it's no longer available. Just search trough the similar items and you should find one. Mine simply wraps the wire around the spark plug wire, and doesn't require batteries. The only con is that it doesn't have a backlight, making it difficult to see in the dark.
You need one with adjustable settings. Effectively your bike fires the plug like a two stroke. I don't know if the one you posted has adjustable settings but this one does. http://www.amazon.com/Trail-Tech-72-A00-Silver-Digital/dp/B00AR2R090/ref=sr_1_1?ie=UTF8&qid=1445393491&sr=8-1&keywords=tto+tach