> I used a fake-battery power adapter and a small DC-DC converter.

Same here. I used to live in a fairly tall building in Manhattan, so found my way to the roof, found an outlet, and would set it up to do timelapses of sunsets over the Hudson.

The camera lens was pretty dirty, so they weren't great, but I enjoyed them: https://www.youtube.com/watch?v=OVpOgP-8c9A

Nearly all Canons have a small access port as part of the battery door, which you can put a power supply cable / through, by design. Don't buy too cheap a dummy battery, the really cheap ones may have very bad voltage regulation. You can get ones designed to work from a USB power bank, or mains.