Orange Rocket is not mounded but I wouldn't call it arching, either - more columnar. You could check it out and see if you like it. The color is great (if that's what you are looking for). 'Admiration' is more delicately formed than some, and smaller - it has dark red leaves with a light border so the effect is of light red. Neither really fit your bill exactly....

Sara

Outlets here present a range of different purple (and yellow) ones every year. Despite Berberis thunbergii being a weed in the East nurseries there continue to select and introduce new forms. Your best bet is to see what outlets have there and make a selection - you can tell the hummocks from the normal ones by how they look in the nursery, see what shade of purple they are even in nursery sizes - or if ordering from elsewhere catalogs/web sites usually indicate what the habit is like, describe the color - although going by photos or statements for the leaf color is not as good as viewing the plants in person.