So if you go of the beten path a little, you'll find this Trabant museum, myself, I found it by chance while riding by with the tram that runs right outside, otherwise I would have missed it. So I really found it all by chance.
The museum is great fun, it is quite small, but they get the story about the Trabi told in a good way. I went on a rainy day and although some of the cars are outside, it still is suitable for a rainy day. It is run, as I understood it, by the local auto mechanic shop residing in the same building, so spoken english is limited, but don't let that scare you away ;-). Upon paying the fee, 100-some kronas, you get an information folder in english, to be returned when the visit is over, but it contains a lot of information.
I am happy that I found this museum and got to visit it while in Prague!