One of the banks (CIBC) I used to use is at the corner of Niagara Blvd. and Princess Street after you cross at the Peace Bridge. Use Google maps to find it. The bank is close to the Bridge/River and easy to find. The May Wah Chinese Restaurant across the street about 100 yards up on the River side of the road is a good one!
When I used to cross at the Rainbow Bridge I would go to the Scotia Bank. Just use Google maps and look for Scotia Bank and Niagara Falls.