Paula Baker's interest in the above journey made me first think of the
recent UK TV series of European train journeys taken by former politician
Michael Portillo, using the old George Bradshaw train schedules. I don't
know if that helps but there is also a series of guides by William Harman
Black, (The real Europe pocket guide-book (number 10 of the "Black's blue
books") with 23 simple outline maps of the 33 new countries, and elaborate
index, by William Harman Black 1920).
https://catalog.hathitrust.org/Record/007685715
The Universities of California and Minnesota may have copies.

Stanley Grossman. Glasgow, Scotland