It takes a little more time to find special Christmas Tree Ornaments rather than just balls or teardrops, but these Bright Blue ones should fill the bill.
I love to use birds and found a couple of them. One of them has a clip on it and could be placed on several branches. And I love love the biplane model. How cute to see it flying around in the branches with the birds.
Whichever one, or several of these five you choose, you will surely love the bright spots of the color in your tree.