Modern Vespa

Or do I need to take apart the whole handlebar setup .

Hello,
this topic is already old, but I only came across it now because my speedometer glass (Plexi) (Supertech with TFT display) also has cracks/scratches.
It may already be known, but in case it's of interest to some of you. After searching around for a while, I found a new plastic housing online from China (costs around 90-100 euros including shipping). I then disassembled the speedometer, or rather cut open the old housing all around to remove the upper cover from the housing with the broken Plexi. After that, I had to carefully remove the upper, thin, dark film with a hot air gun and a carpet knife, because it's glued. Underneath are 4 Torx screws (Torx size 6), which have to be removed because these are the screws that secure the circuit board to the rear housing cover. Then screw the new housing back onto the circuit board, stick the film back on, glue the housing together... done.
As I said, maybe one of you has the same problem and I can help you.