Basically a 1-1/2 liter bottle (*very* tall), inverted, buried into the bucket with the tomato plants, with a hole drilled in the top for re-filling. These bottles will deliver the water at the roots vs. at the top, or on the leaves, because, as I have learned, tomato leaves and water don't play nice.
Because I was limited in my space, the 2 liter bottles wouldn't work. I needed something very tall, and relatively narrow. The Jana water bottles did the trick.
A little hole drilled for refilling, and I'm set.
Thanks to good friends Ann and Nancy for their suggestion.