Like Norman, I like a bar end mirror on each end of the handlebars. As I have Eglis (a Godet twin and a Smith single) my front indicators are the mounting bolts for the head lamp. and the rear ones (on the twin) are on a cross bracket mounted behind the rear number plate, and (on the Comet) on wide brackets to the rear of a custom made carrier.
Donkeys years ago I made flashers that fitted on a band round the wrist of my riding gauntlets. A flat 6 volt bell battery provided the power and the "flashing" was produced by having a flat contact on thumb and first finger and I simply opened and closed my finger and thumb! with my arm outstretched! It was quite good really, considering it was about 1000 years before flashers were regularly fitted to bikes. I;ve no idea what happened to it but I still have my large Brown leather gauntlets, they in turn have a white reflective disc on an elastic band round the wrist. You stuck your hand out and the" candle glow " from the car behind lit up the disc Modern technology at it's simple best!!!