Well, won't that require a different identity? My personal email account is funny-nickname@gmail but my work email is my-real-name@work. Github used to allow/encourage multiple identities but then changed it because it was super confusing and hard to manage. Maybe they've fixed that now. :/
They fixed some awkward "custom routing" screens a while ago. I've been using my single account with different companies for years now. I just make sure my git `config.email` is set right, set GitHub to route notifications for work repos to my work email, and it's done.
I've also been the admin on those Business accounts. It's easy.