Brake conversion on 1958 PV444

[Boobtube]

I was wondering if it's possible without too much expense to convert the single circuit braking system on my 58 pv444 to a dual circuit system. Is there a drop-in master cylinder that can replace the current one that would allow me to use pretty much the same plumbing that's there? I want the added safety of a dual circuit system. I'm not looking to convert to disc brakes.
Thanks