Help - bag storage around Front Street

On Monday I have meetings in Northern Ontario. I will be flying back to Toronto in the evening (Billy Bishop) and have an engagement that I need to attend that evening where I can't take my luggage. I will be about a 5 minute walk from Union. I'm cutting the time close already so I don't have time to run home and drop it off.

Where can I put my bag?

I know this question has been asked a number of times, but I can't find an actual answer. I don't mind paying, but I have no idea what the options are.