I quess I am wondering "WHY" do you want cherry blossom honey? I know with the food I eat I like variety. You curious what it tastes like or is there a medicinal reasons. The Varietals with several flavors has a wider range of flavors present. I concur in early spring one would need to add supers the day prior to the blossoms and remove the day after. Cherry bloom is short as well.
good luck, let us know if you find a way. In Michigan there are a large number of cherry trees in the Traverse City area, one could either inquire about or offer your hives there.