Thank you for the photos. Worth far more than 1000 words.
from the photos I think you have a 3/8 inch aluminum line. Or it could be 1/2 inch. Because the evaporators are fabricated here in California I suspect they are standard number six and number eight flare fittings. I don’t believe metric comes into the equation.
you might have to hunt to find one with 5/8 inch barb, or use more than one fitting, combined to create what you need