I finally found it!
I found this title with english subtitles available from http://www.ebay.com/itm/Tajemstvi-Oceloveho-mesta-DVD-1978-Czechoslovakia-Sci-Fi-Film-/131380958915?hash=item1e96ea56c3
this dvd is also available from czechmovie.com
http://czechmovie.com/d/tajemstvi-oceloveho-mesta-the-secret-of-steel-city-dvd-1000065/