My website (the one you’re reading) now supports HTTPS(ish)! HTTPiSh™ for short.
GitHub Pages (which hosts this site) doesn’t ordinarily support SSL on custom domains (yet), but you can add it using Cloudflare’s Universal SSL.
And it’s free and really easy to do, both things I didn’t realize (and mistakenly led to my tardiness here). Here are a couple good walkthroughs to set it up (1, 2).
I know this isn’t the perfect solution – while the connection between the user and Cloudflare is now encrypted, the Cloudflare ↔ GitHub connection is not (more info here) – but at least it’s better than a sharp stick in the eye.