This youtube video shows a device that one can use to sample varroa in the same way you would do an ether roll or alcohol shake, but this method doesn’t kill the bees. It knocks them out with carbon dioxide and then they recover after about five minutes. The CO2 knocks out the varroa as well so they fall off the bees and can be counted.
However, this research paper suggests that the CO2 may not be that effective at knock out the mites (http://www.apidologie.org/articles/apido/abs/2001/02/fakhim/fakhim.html). Obviously it does in the video to some extent, but it would be nice to see an alcohol wash done on that sample of bees afterwards to see how many were missed by this method.