This is a linkpost for http://sites.stat.psu.edu/~babu/nash/money.pdf
Are there any other documents by Nash on the subject other than this lecture?
The lecture mentions an earlier paper with "Ideal Money" in the title and indicates that some of the things you might expect Nash to say about "ideal money" are not covered in the lecture because they're in the earlier paper. If you have access to JSTOR you can find it there. It's from 2001.