Mathew Hobson is a sales associate at The Flag Shop, a 30-year-old business that sells a myriad of flags and banners — all of which are made in Canada — out of its Osborne Street location.

Tammy Quantrell, owner of Kennedy’s Flags in Erin, which has been in business since 1947, said she first noticed “a big uptick” in Canada flag sales around Feb. 15, which marked the 50th ...