Ignacio Sánchez brought to my attention the Australian company Teenix. They provide replacement board for the HP55, HP65 and HP67 calculators. If you have a broken HP67 calculato, your best bet is to call Teenix and get a board for the calculator. It is a direct drop-in change that will revitalize your calculator. Think about, for example, continuous memory!
I will copy from Teenix's website the feautres of the replacement cards:
Note: These CPU boards will not fix problems with the display, keyboard or card reader components, however
if the card reader has failed, you can save and recall programs using internal storage memory.
Teenix also maintains and provides diverse software emulators for said classic calculators: MultiCalc.zip
As I have a Mac I (and I am overflown with repairs), I have not yet tested the emulator, but it covers apparently all the classic models. Scroll down in the main page to see what we're talking about: you will stay for a long, long time in the website!