Perhaps blended green peas? Not quite the same, but a similar texture and appearance, at least.
I found this with a quick google: bubblechild.com/2011/08/24/inspiration-avo
Avocado is generally used as a source of healthy fats, so if you don't want or can't have it, one of the other healthy fats could work. Nuts, olive oil, or peanut butter are all alternatives.
Be sure and ask on the Spark Solution team, too!