I coded one up in Z3's Python bindings using the new Optimize functionality.
def min_dom_set(graph):
"""Try to dominate the graph with the least number of verticies possible"""
s = Optimize()
nodes_colors = dict((node_name, Int('k%r' % node_name)) for node_name in graph.nodes())
for node in graph.nodes():
s.add(And(nodes_colors[node] >= 0, nodes_colors[node] <= 1)) # dominator or not
dom_neighbor = Sum ([ (nodes_colors[j]) for j in graph.neighbors(node) ])
s.add(Sum(nodes_colors[node], dom_neighbor ) >= 1 )
s.minimize( Sum([ nodes_colors[y] for y in graph.nodes() ]) )
if s.check() == sat:
m = s.model()
return dict((name, m[color].as_long()) for name, color in nodes_colors.iteritems())
raise Exception('Could not find a solution.')