I love RPN, and dread the day that my HP15C dies. I got it in 1985, after the bookstore guy showed me how the stack entries lift and drop, and I have been sold on RPN ever since. Some years back I wanted a graphing calculator, but couldn’t find one with RPN.
Once you go RPN, you’ll never go back.
HP put out a "Limited Edition" 15C. I bought one last year for about $100. My original goes back to 1984, the display on it is going bad, and replacement is an "advanced level" task.
Not quite the same quality on the keypad, but not bad.