How about a Casio PB-2000C, in all its pocketable 910 kHz glory, up to 64k RAM shared between heap, stack, code and RAM filesystem. 192 x 32 LCD and a piezo buzzer. Serial and parallel ports available and a FDD. It also has a ROM card slot. And a card was developed, the only third-party ROM for this platform, by one Hans Larsson in Sweden, in the late 1980s.
A 64k ROM with:
- a mostly TP 5.5 compatible Pascal compiler, crt and friends
- inline assembly
- units, loadable libraries and all
- debugger
- full-screen editor, global search and replace, etc.
- visual file manager
- CLI with redirection and rudimentary shell scripting - variables, conditionals, arguments
While the hardware platform is somewhat available and there is a very good emulator, due to "issues", the DL-Pascal ROM is not at this time publicly available and only a chosen few have access to it. Luckily there is a preservation effort underway.