Many PSP parts can be ordered separately.
A few examples:

- LCD screen, new, with backlight, for the old model PSP: 55 euro
- LCD screen, new, with backlight, for the new model PSP: 75 euro
- Analog joystick complete with the nub: 12,50 euro
- Analog joystick, just the nub: 2,50 euro

If the part you need isn't listed, ask for information through the contact page.