I am looking into buying a scooter (like a Vespa type scooters) and want to look at a buyers guide to help me choose which one is best. Is there any main buyer or just regular guide for scooters. I am looking for something like a Consumer Reports but with more information on styles and what kind of scooter is best for what. Something that also includes info on accessories like side cars.

Consumer Reports is planning on doing something on scooters and motorcycles but nothing yet. You are going to have to do your own work based on what is best for you. There are lots of scooter forums but you need to look for the ones that aren't brand based since they will, of course, say what they have its the best.
Things will vary a lot based on your needs. Study up carefully or you will be looking for a new scooter pretty quick after buying your first!