To purchase and setup ahead of time from Canada, here are some roaming options.
Based out of Toronto. You can order from them or from Amazon. They have both SIM cards as well as SIM “stickers”, which you put on top of your existing SIM card. Here’s some background on Quora aboutSIM stickers.
Not global, but great for Canadians going to the US. Either $5CAD per day for unlimited, or about $68CAD per month,