You could use ramekins and place them on the cage floor if you´re in a pinch.
You know I have to feed my true bonded lovebird pair vegetables separately, so one bowl is on the lower corner on one side, and the other bowl in the upper other side corner. They don´t eat fresh foods well together.
As for my other pairs, I give them rabbit dishes (12cm bowls) for veggies so they have space from each other but still benefit from eating together.
They are all fine eating seed and pellets from the same smaller bowls, but they love veggies so much that they can bicker over them.