Actually, Cloudflare offer you certs they sign (which wouldn't be trusted by others, but they verify), that you can use to encrypt from the server to them. You still have to trust Cloudflare, but it's not plain text from cloudflare to your server.

If you mean the case where you literally can't serve under HTTPS, it's not just getting the cert that is the problem, in most cases running a local proxy of something that will would fix it, although I accept there are cases (cheap shared hosting, I guess) where that's not an option.