As expected the Shopper Drug Mart portal is showing available #covid19 appointments for high-risk groups (more being added throughout day/week): https://shoppersdrugmart.medmeapp.com/schedule/activity-groups/COVID-19-Vaccine
If asked, the minimum interval is 84 days since previous dose as mentioned on https://www.ontario.ca/page/covid-19-vaccines#completed-initial-series (screenshot below if needed)

