I know the tool retired with the last catalog - it was called a "color spritzer tool". I have one, and it works great with watercolor markers, if they have a brush tip and are juicy enough. It takes a lot of squeezin, though, to get a nice background
The tool was also called a "blitzer" back in the day and you used to be able to get them from other places. Not sure how available they still are, though.