I have a seatpost blinky and a blinky on my backpack. Like the one you mentioned it can be mounted to the bike and has a clip. The backpack is a bookbag/daypack style so I added some reflective tape down the front of it.

"Over the top"....absolutely not!. Search the forum...two front/two rear seems to be a stanard configuration. But your mileage may vary.

A portion of my commute is on a farily busy highway. A third rear blinky may be in my future...and some more reflective tape.