Hello. I visit the niagara region at least once a year it's usually a pain trying to find veg friendly restaurants to eat at. great for wine touring though.
I currently live in the London area though.
I feel your pain! We used to have an awesome Chineses restaurant in Niagara Falls called Xin Vego- strictly vegetarian! Amazing- too bad it's now gone.
The Spice of Life in St.Catharines has some great options. If you visit in Sept. during the grape and wine festival there are a lot of options offered by some of the local restaurants who set up shop at the festival and offer samples. Plus there is the wine which doesn't hurt
Buffalo, NY seems to have a few options- i.e., a restaurant called "Off the Wall" makes awesome Buffalo style egg-plant wings!