In search of a Droya(?) emigrant

Hi. My search through our family tree has led to a possible connection to Druya. In the US, our great-grandfather was known as Hyman Kaiser - Hyman Isaac Kaiser He was born in 1890, and we believe emigrated to the US (Philadelphia) around 1905. The family "legend" is that his family paid to send him to the US to escape military service (he was Jewish-would this have been a risk?). We also think the family name might have been something like Kaiserez or Kaisericz (maybe Kozoroff?), but we don't know. He may also have had a true first or middle name of Isaac.

We have just come across the possible connection to Druya (we never knew the town he was from). His US WWII draft card lists a birthplace as Droya, Russia.

Does anyone have other suggestions on how we can follow this path and learn more about his life and family?

Thanks so much. - David