See some papers following
Ehlers, P.J. and Porter, T. Varieties of simplicial groupoids. I. Crossed complexes. J. Pure Appl. Algebra 120~(3) (1997) 221--233.
(which you may already have).
As another example, given a double groupoid, it's simplicial nerve in one direction is a simplicial groupoid in your sense. There are lots of examples of double groupoids, see for example my arXiv paper 0903.2627.