While not quite the real deal, the aerodynamic test vehicle OK-GLI is at the Technik Museum Speyer in the same-named German City, open to the public (the nearby (30min; car) museum in Sinzheim has a both the french and soviet supersonic passenger planes (Concorde/Tu-144) in it's exhibit).
I can recommend both museums (interests have to match, of course).
[0]: https://en.wikipedia.org/wiki/OK-GLI