Another Rad Ref librarian found a website on Iranian anarchism from znet:interview with Payman Piedar, the editor of Nakhdar, a Farsi/English-language anarchist-communist magazine(2005).
Another site mentions the names of Kacha and Mares in relation to Kafka, others include a general Czech anarchist history and an ANARCHOPEDIA article on the Czech Republic
Google Scholar only gets 2 hits for: "Michal Mares" "Michal Kacha", and I would plow pretty thoroughly through the "30 hits" (14 unique ones) that a regular Google web seach gets gets. Even the ones in foreign languages might give names and places that could be leads (even try www.google.cz, if you want to try guessing at some Czech language ones). The same search gets 3 hits in Google Books and I would go with the broader search: michal mares kachka (5 books). All 5 are restricted books (under copyright), but Open Worldcat will let you search their titles, to find the libraries nearest to your computer or network provider that own them.