Since the Bells of Ireland are fairly small it might be easier to hollow out a cone of gumpaste and thin it until it takes on the shape of the flower. Essentially thin it by rolling a small cel stick on the gumpaste while keeping the base a little heavier.
I don't know how well a Calla cutter would work. Callas don't open the same way, so you would have to use two pieces to get the proper shape. Even with that, the seams are going to show and will probably be a bear to stick together in a cup shape.
Thanks, Michele. I've never seen them, so I didn't realize that they were so small. I'll probably just stick with the roses and gerbera's.