I bought a HP29C when I started my engineering course.
They were pretty good. Aside from not having a card reader (so you had to manually enter programs each time), they were not that far off the top of the line model – the HP67. One plus was it had “continuous memory”. This meant that it would retain the program; even if you switched it off. See www.hpmuseum.org for details.
Recently, I wrote an emulator for the HP29C. It looks like, and is supposed to behave like, the real thing. It even retains programs if you switch it off and on again later. Hopefully it’s pretty close to the real thing. There are additional actions available if you tap the emulator screen.