Everything you need is access to PlayStation Now.
While a proper sequel to the Red Dead Redemption is on the horizon (Fall 2017), the original game was announced as part of the PlayStation Now catalogue back in October. As of today, active subscribers are allowed to play the game both on PS4 and PC.
The Undead Nightmare is also available in the form of a stand-alone DLC. If you are interested in both titles, go and grab your subscription. VG247 reports that one-year plan is now on sale for $99.99.
Red Dead Redemption was originally released in 2010. Current-gen players were able to play it using Backward Compatibility on Xbox One.