searching for a relative who had a business in Rivne in 1939 #holocaust #ukraine


I would appreciate suggestions on next steps in searching information about a relative (great uncle) who I believe likely died in the Shoah. The last name is BRONSZTEJN, first initial S. (I thought the name was Simon, but it may have been Srul). He was probably born in the 1870s, probably in Ostrog/Ostroh.
I have a copy of a business envelope postmarked 1939 for his business (glassware) under the name Bronsztejn, S., located at 8 Pocztowa (Post Office Street) in Rovno. Recently I found online a 1939 list of Jewish businesses in Rivno which included Srul Brojnsztejn at 8 Pocztowa, which made me wonder if his name was Srul, not Simon. 
From the USHMM, I found the name of Srul Brojnsztejn of Warsaw, not Rovno, on a list of Jewish survivors.
In 2004, I wrote to the Red Cross Holocaust victims tracing center seeking information about Simon Bronsztejn. They apparently corresponded with the archives in Rovno. The archives forwarded a letter in 2004 stating that “in the list of  Jewish population of Rovno as of January 15, 1942 the name of Simon (Shimon) Bronshtein could not be found.” It also said “in the book of Ukrainian Grief of Rovno Region, Rovno, of the year 2002, Khaya Bronshtein is listed as an owner of the building at 8 Post Office Street during the years of 1937-38. It is further stated that she was shot by the German fascist occupiers in November 1941.”
At Yad Vashem, there is a page of testimony regarding Chaya Brojnsztejn of Rovno, stating that she was killed in 1942 in Rovno. There also two other listings  for Khaya Bronshteyn of Rovno without documents attached, one of which refers to a list of persons evacuated to Uzbekistan and the other of which states presumably murdered in the Shoah.   
I would appreciate any suggestions anyone may have regarding possible next steps and follow up, including the name of a researcher who could check property and other records in Rivne, if they exist. Or online sources I can check myself. 
Many thanks. 
Howard Brown
Stowe, VT
Researching BRONSZTEJN in Ostrog, Rivne and Warsaw, SHIKHMAN  in Makariv and Kiev, and SHVETS in Makariv.

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