Still got and use my 12C, and 48gx, unfortunately sold my 28 to buy the latter. When you look at the quality of what HP used to produce versus now, it's very sad.
I sniped a 48SX on a Craigslist equivalent for 20$, the guy even sold the full manual and 3 math/asm books, I couldn't resist.
I'm learning electronics, I plan to mod it if I can, maybe an ESP8266 "coprocessor", a rechargeable lithium bat. and a usb port.