Hi Janice,

You might also try contacting Uncle Tom's Cabin museum:

http://www.uncletomscabin.org/homepg.htm

I believe that the curator is Adrienne Shadd who has done extensive Ontario research, and might be able to help you further.

Also, have you read "The Blacks in Canada: A History" by Robin W. Winks? There are a number of references to William P. Newman.

Hope this helps.