Finding a paper by John von Neumann written in 1951

I ran into a similar problem recently, and my solution was to email the NIST archives and request the article be scanned and emailed.

I received an email with a pdf version, and now it has been recently added to Richard Arratia's list of hard to find papers. https://dornsifecms.usc.edu/richard-arratia-usc/hard-to-find-papers-i-admire/

One of the citations gives the bibliographic info,

von Neumann J, Various Techniques Used in Connection with Random Digits, Notes by G E Forsythe, National Bureau of Standards Applied Math Series, 12 (1951) pp 36-38. Reprinted in von Neumann's Collected Works, 5 (1963), Pergamon Press pp 768-770.

That should be enough information for any librarian to find you a copy.