In this wonderful video Schiff plays a second Menuet that I cannot find online (for example in IMSLP). Two questions:
- How come it is so? are there multiple versions of these pieces? If so, what's the history behind it?
- Can I find it online?
This second minuet actually is available on IMSLP:
As for the multiple versions, we don't really know. All we know is that there are several surviving manuscripts of these suites, some written by Bach and some not, and so it's difficult to determine the "definitive" edition. As such, it is up to the performer to either decide which minuet to play or to go ahead and play both of them. The minuet in question is only present in later sources.
A decent summary of the situation is given on this page under "Process of Compilation and Revision."