As long as Vercel (formerly Now) CLI does not support being run behind a proxy (see vercel/vercel#255) you can do so with this small wrapper.
Uninstall vercel!
npm r -g vercel
Install proxify-vercel:
npm i -g proxify-vercel
Set your http_proxy, https_proxy and no_proxy environment variables.
Start using Vercel (formerly Now) CLI with support for http_proxy, https_proxy and no_proxy:
vercel <any Vercel (formerly Now) CLI commands>
proxify-vercel runs Vercel (formerly Now) CLI with global-agent preloaded. global-agent adds proxy support to any http agent running in the process.
This is a fork of the wrapper for Now that respects proxy environment variables by Martin Knopf.