The key phrase for this is "Fridays for future" and you can find a map here:
https://www.fridaysforfuture.org/events/map
Oddly it looks like there are weekly sit-ins in Nanaimo, Port Alberni, and Campbell River, but not Victoria. But if you're in Victoria there's no reason not to do it yourself, just go sit on the lawn of the parliament building with a sign. Submit it to the website or do it long enough and people may join you.