TN live/work in US doing business in Cdn?

Can a Canadian living and working in the US on TN status also do business with Canadian sources from within the US?

Not unless the work is covered by your TN-1. Where you physically are is what counts for immigration purposes, you can't for example visit the US as a B-2 visitor and remotely work for someone in Canada over the internet. The non-immigrant category that sort of covers this situation is E-1.