Is the Prime suitable, for me

[Dave Britten]

I also wish that RPL retained some of the unstructured conventions of RPN keystroke programming (I majored in CS, so I love having high-level flow control blocks, but sometimes a quick GOTO would be so handy for a simple program.) That 48SX text editor is just so damn slow with large programs, though. Splitting them into small, possibly reusable routines is a must sometimes. The 48 does give you the choice of creating RPL programs or algebraic user-defined functions, which is nice. Keep a tiny Moleskine notebook in your 48's case to document programs; RPL has no way to insert comments, and with no label names to assist you, the code becomes very opaque very quickly. At least you can use long variable names if you're willing to sacrifice a few more bytes of program size.

Have you ever considered the HP palmtops? You can load your favorite DOS-based IDEs and compilers onto a CF card (I have QuickBASIC 4.5 and Borland Turbo C on my 200LX), then also have a hybrid functional/imperative environment with built-in Lotus 1-2-3 and its macros, and a simple functional/equation based system with the included HP Calc solver app (it's basically a 19BII). You won't really get much interop between programming environments, though. Maybe a little bit between Turbo C and Turbo Pascal if you're feeling adventurous and are willing to wrangle the calling conventions. If there were a good DOS version of Free42, that would be really awesome. You can make nice user-friendly data entry and analysis tools with Lotus if you're willing to learn the macro language, which is very much like a calculator's keystroke programming. I've yet to see a better mobile spreadsheet even 20+ years on.

Other totally random ideas:

The TI-74 BASICalc has a Pascal module available, giving you two languages to choose from. Only 8 KB RAM built in, though.

If you search for "pocket computer" on ebay, you'll find many Japanese handhelds with various combinations of BASIC, CASL (whatever that is), C, and assembler. I've never used one, and I imagine the Japanese documentation would be a little daunting, but I'm always tempted to get one to experiment with. Maybe some day.

I still think an iOS device with an assortment of calculators and development environments can prove extremely useful, even though you won't get any interop. Don't underestimate an iPad Mini loaded with Codea and emulators/simulators for an HP 41, HP 42S, TI-59, TI-95, etc. Plus it can do a hell of a lot of other things, too.

You could also find an old Palm OS device such as the IIIxe or m500 and load it with Free42 and Pocket C. Finding one with a digitizer that isn't knackered can be tough at times, though.

The old non-touchscreen Sharp Wizards have a "Scientific Computer" card that gives you BASIC and 32 KB RAM. I think there's a three-dimensional spreadsheet card as well. I'm sure it's no Lotus 1-2-3, of course.

The TI-92/89 family has a very nice programming environment. It's the usual TI BASIC, but with quite a bit more capability than other TI models. You can create programs, or functions which can return values (but can't side-effect). Of these, the 92+ or Voyage 200 would be the better option, as the OS was really designed around having a QWERTY keyboard constantly available.