Depends what you are using it for. occasional personal use or production work.
If all you need is to make a few notches, then a drill press and a hole saw works great. You can use the hole saw without the drill press, you just need to leave extra length so the hole saw cuts a round hole and stabilizes the saw.
If you want a more professional type there are plenty of manufactures making them, but they are quite costly.
Pro Tools has a couple, one of which will do an offset notch.
