Bike light fail

Tuesdays I often ride with Ben. Coffee at 'Diva' on Swann Rd.  Then across the green bridge. Ben goes to the city and I go to Syndetic. 

Last Tuesday evening, I'm about 1/4 home and suddenly my head light goes out. Riding in the dark is illegal and me thinks a bit dangerous.  I persist for a bit considering options.

Perhaps call into a servo or convenience store and buying a torch. Then I hit on the idea of seeing if I could download an app that would make the flash LED on my phone flash