I looked around on the internet and found a remarkable site called Kramerius. After searching under "Louise Brooks" I got more than 100 relevant results - mostly articles, advertisements and images. What I found can be found here.
However, not being a Czech citizen, I am not able to view the results. Seemingly, they are only available to patrons of the National Library of the Czech Republic, or to Czech citizens able to request prints. How frustrating, as these search results promise to be quite exciting. Can anyone help? Are there any Czech citizens able to visit the National Library of the Czech Republic?