If I was still playing 4's I'd be looking for a good used 2010 or later Fender Am Std with some budget left over for upgrades, if they were needed.
IMO Fender make it more difficult for 5 string players to go for their P basses. The Roscoe Beck was a great bass but obviously didn't sell enough. I think they should have stuck with it but who knows why Fender make the decisions they do!
There are some fabulous 5 string P basses out there, unfortunately and sadly, because I've been a Fender fan for the last 50 years, non of them are being made by Fender.