I wanted to provide an update to the group on this request since I think the findings are broadly applicable. First, thanks to all who took their time to take a look and offer their help and suggestions. In particular, Yale noticed that there is a very slight handwriting difference between the 'O' in Osernovitz and the 'O' in Ornstein. That combined with the lack of likely candidates for the town other than my initial assumption of the well-known Czernowitz, caused me to revisit the Czernowitz vital records index (an amazing resource at https://czernowitz.geneasearch.net/ if you were not aware and haven't used it).
I took a more careful look at the indexed records and indeed found his birth record as Ahron Ber Orenstein (I knew his Hebrew name from his matzeva as Aharon Dov). The date is off by a few years from what is provided on his naturalization, but the month is the same and the mother's name is correct. Since the parents did not have a civil marriage, this is the only record I've found that mentions the father's name, but I knew it was Ire / Uri and is listed here as Isser.
Can any of the German speakers in the group read Isser's occupation (https://www.familysearch.org/ark:/61903/3:1:3Q9M-CS9R-1WDT-3?cat=1378569)? It's the record on December 23 for Ahron Ber in house 1225.
I also want to thank Giannis who was able to find the passenger manifests for the family. Again, Benjamin's naturalization was partially correct . . . the ship name was correct, but the dates were not. Since that is a common error I thought it was off by a year, focused on that ship and gave up when I couldn't find him even after looking at all of the indexed male names. It turns out he was on the same ship the following month, indexed as Berl Hormstein/Homstein. His wife and children followed through England about 2 years later, indexed as Crustein/Orustein.
So . . . keep looking . . . the records are out there!
Chicago, IL USA