I had exactly this problem with my replacement electronic unit. I wired a piezo-electric sounder across the terminals of the flasher unit. It gives a nice clicking sound just like a modern Renault . This only works with bulb units btw not LEDs.
Now the slight problem is that I bought it from Maplins who have now sadly gone.
If you drop me a PM with an address I'll see what I can find and send to you.
And yes the flasher unit is the one behind the dash with the light green /brown wire and the Light green/ grey wires going to it.
Tony.