I recently completed a turn sig mod that proved to be simple and non invasive to the GT200 scoot that is my pride and joy.
Unfortunately I did not take pictures, so I hope my description will suffice.

I purchased 2 R/S piezo buzzers #273-075 (specs) 3200 Hz +/- 500Hz
9 - 28 VDC @ 105db.

These were fitted to the turn signal housing with double sided foam tape.
They were adhesed to the housing, just below the bulb connector. The yellow wire was clipped off as I did not want the warble function, only clear tone. The remaining leads were red+ and black -.

I removed the connector to the bulb in the housing and ran the leads from the buzzer through the channel under the release tab of the connector.

I then stripped 1/4 in of insulation from the buzzer leads and inserted them into the female tabs of the connector. The only thing to remember is black to black to observe correct polarity. The red lead goes to the other tab, no matter its colour.
I then re-attached it to the male connector of the bulb housing. The re-assembly was per normal as everything fitted to a T.

The only problem was the 105db sound level. It scared the hell out of women and small children while stopped at a corner making a turn. Actually, It scared the hell out of me, first time around.

The solution to this, was to fill the opening of the buzzer with silicone sealant. This reduced the output to an acceptable level.
The only complainants now are the neighbourhood dogs.

This type of mod, which there have been several postings for, is really a good safety point.
It is the next best thing to self cancelling turn sigs. There are several conversions available as after market, but do not work on the existing Vespa switches.

I am trying to adapt a momentary contact switch arrangement to the Vespa circuit. If it proves successful, self cancelling modules should work.

I will post any info if it works out.