Look for "Sangaria Melon Soda" here in the states. Sangaria is same company that makes ramune sold here in the states, so if you can find ramune you can probably find the Melon Soda at your Japanese/Asian grocery store.

Like this below:
http://www.wizzywig.com/xcart/produc...roductid=41695

It's clear - has no color. If you want the "cream soda" taste and look from Japan, need to add a little bit of green food coloring and vanilla ice cream.