Ground Cover to tread on

I just read the Over the Fence section in Aug. issue that arrived today.  I use Mazus (false snapdragon) between my stepping stones as well as in other places.  I originally got it from a friend who was destroying it to enlarge a pond.  I rolled it up like a carpet in several sections....it is VERY shallow rooted...and unrolled it and watered it in.  It thrived.  I have since put it everywhere between my stepping stones and as ground cover.  It is covered with a small purple flower in spring.  Everyone wants to know what it is and where to get it.  I have given it away to many visitors to my garden.  I live in Zone 5A