My 5 years elder brother and I were both engineering students. In 1971 he had a $400 HP with RPN. In 1976 I had a $79 TI with algebraic. Both could do the same calculations but worked differently. When did RPN leave the market? I never noticed it.
This article from 2007, implies that HP was going to release a handheld, A New HP Calculator for RPN Nerds, but, alas, the link it points to is dead.
As of 2011, Hewlett-Packard is producing the calculator models 12C, 12C Platinum, 17BII, 20B (financial), 30B (business), 33S, 35S, 48GII and 50G (scientific) which support RPN.
I have a 48SX emulator app for my android phone. Almost as good as the real thing.