So up front based on my research thus far this is a long shot.  Is there such a thing as a spray treatment to kill off paspalum in otherwise healthy lawns?

Over the last couple of years our lawns have developed paspalum thanks to wind blown seeds from the neighbour.  I've done a bit of research and found a brush on gel from Kiwi Care (Mitre10) that goes on the crown of the weed.  It does kill it - and a chunk of surrounding grass but new clumps of paspalum is coming up faster than I can kill them.  The only other solutions are dig the weeds out by hand or spray the whole lawn with Roundup or similar and resow the grass.  Problem is the seeds will keep coming and continually killing as they appear and resowing isn't feasible for ever more.

Is there a spray similar to Weed 'n' Feed that just attacks weeds including paspalum leaving the grass to do its thing?