All three versions of the Mysterious Stranger story were published
together in _Mark Twain's Mysterious Stranger Manuscripts_ (Berkeley & Los
Angeles:  University of California Press, 1969). This book is out of
print, but it should be in any research library. I don't know if it's out
of print for good, or just pro tem. In addition to all three texts, it
gives a full run-down on who did what and how the three versions are
related.

_No. 44, The Mysterious Stranger_ (Berkeley, Los Angeles, & London:
University of California Press, 1982), which reproduces the text of "No.
44" from the 1969 work, but not the scholarly introductions and notes, is
in print: $40 for cloth, $13.95 for paper.

Kenneth M. Sanderson
Mark Twain Project