StazOn would work...the Memento inks also work. I use Memento with both Copic markers and colouring pencils that I blend with odorless white spiritus. For watercolour, you get best results with aquarel papers. As far as I know, both StazOn and Memento work that way aswell. I've tried Memento on aquarel paper in combination with Distress Ink colouring. It didnt run the stamped image. With both inks you really cant go wrong as both leave crisp stamped images. And both sell in different colours too.

Good luck