Prom Portugal here , there is a thing i am searching for but there are no news since 2012 the same principle of making any bike eletric for 500$ adding Eletric motors to the wheels , there was a guy in the US that made it ....https://www.youtube.com/watch?v=qxn6XdLIb7U... but i can't find any thing about it if this thing was in the market for the "3000$" they said everyone would have one now i think and EV is still very expensive and in Portugal there is a law that u have to rent the batteries =S that means we pay more to ride an EV than a normal car ...
There are a lot of reasons why you do not see these kits as a mass market item in cars while it is common in bikes. Bikes have almost universally standardized parts across most brands that items can be connected to, cars do not. Secondly electric motors for cars are massive, the force needed to move a 200-300 pound object 10mph is far less than the motor needed to move a 2,500-4,000 pound object 35mph, and electric motors do not scale linearly in size when increasing power. that being said there are options out there for you, it just means paying someone to do custom work for you or you doing the custom work. Here are some links.