Scooter conversion to electric for errands

Hi all,

I have been lurking for a while but this is my first post. I am interested in purchasing a 50cc scooter in non-running condition (to keep it cheap), taking out all the gasoline-related parts, and converting it into an electric scooter for doing errands and such within a couple miles from my house (there is a huge shopping center maybe 1/2 mile down the street).

I am talking about a normal scooter, like something that looks like this. I don't need anything fancy but I would like a top speed of 40 mph just to be safe (the speed limits on the roads I would be using are 35 mph). I'd also like to do it with a fixed-ratio chain drive if possible so that I wouldn't have to get into all the complications of having a transmission. Maybe with a motor like this?

Is this realistic? I have been looking on the web for some time but I have not found much in the way of comprehensive guides or build threads covering what I want to do. This one is OK but it uses a gearbox and I am afraid to get that complicated on my first build. Can anyone point me in a decent direction?

Thanks!