I have a couple of these, but have had no need to find a VIN # , as I have not attempted to register them in the States.
Being Sans Permis cars means that they are not registerable, nor need to be registered to be driven in France.
Therefore, a VIN # is somewhat superfluous / not required to be provided by the manufacturer or persons intending to drive one in France.
So there is the possibility that it has none.
But seeing that yours is 75 cc over the Sans Permis (presuming it not to be a diesel) limit, it seems more likely that it should have a VIN.
Nevertheless, I will have a look about mine in the near future.
Have you checked for a placard riveted to the flooring under the seat, and near the battery box yet?