Until you find something suitable, here's a thought:
Most greens/whites that are bulky can be measured as 2 tsp/6 oz water. Three teaspoons are equal to one tablespoon. When you measure a tablespoon of tea leaves, you get roughly two teaspoons of tea leaves - in my experience there's about one teaspoon of wasted space in each tablespoon. (I hope this makes sense.)
So, in the meantime, you can use a tablespoon measure for your greens/whites.
On a similar note, there's this scoop
, which is perfect for making one pot of tea. You could use two scoops to make a pot of green/white tea. I have the "One Perfect Cup of Tea"