I just checked the South Africa Jewish Rootsbank. It a genealogy site about South African Immigration and Genealogy.
It may be a long shot - I typed in Lasker into the general search.
There are a few entries about an Isadore Lasker who appears to have lived and married in Barberton in1890 and also an entry about a death in Durban in 1928.
Here is the link http://www.jewishroots.uct.ac.za/
A quick search of the South African National Archives shows an Isador Lasker applying for Naturalization in 1906!
There may be other entries if you take time to search. This may or may not be the same person but it is tantalizing!
By the way, Barberton in South Africa is a gold mining town.