Tobikko is probably what you are looking for. It is the most commonly used cheap garnish for restaurants in areas like yours. It is flying fish roe. Curing is done in saltwater (not likely bad for your mandarin). The stuff that is yellow, has yellow dye, red, red dye, green, well you get the idea. I really doubt that food coloring is all that bad for a fish either. As far as other preservitives go, that will be a case by case basis, as far as the brands go but must be printed on the jar.
I am familiar with most of the fish suppliers in Seattle (the ones that those restaurants buy from), and thought you might be interested in "the purest stuff", which to me reads fresh, not in a jar. Regardless, tobikko can most likely be found at Safeway or a Larry's Market by the anchovies.
You could also try DT's oyster eggs first though.