Any decent digital audio mixer should be able to add a delay to any of it's independent outputs. They usually go up to 250ms or even more. That's roughly 15 video frames at 60fps or 7 video frames at 30fps.
As you said many devices can offer delay. But I wonder if products from video manufacturers (AS22S Rane, VA-256xl Kramer...) have something more than common delays.
Both devices that you mention seem to be able to delay the audio and could be be a good solution in case your audio mixer does not offer that possibility.