The ribbon cable is now unavailable at Pioneer and all of the parts stores that I have found. However, I did get one from a third party who is producing their own, supposedly improved, version. They are selling them for $70 on ebay:
http://stores.ebay.com/SAME-DAY-AUTO-AU ... R-SERVICES
This worked for me and fixed my problems (blank screen, some buttons on front panel not working, and then later the screen not coming out).
However, as previous posts mention, be very careful about not breaking the switch. The service manual suggests holding it down if you need to slide the screen unit back into the chassis. I broke my switch while doing this. What the manual doesn't say is that the switch should be pushed down by gently pushing it from the right-hand side (as you look at the exposed circuit board). If you push it down from the top (like I did) then you can easily apply too much force and break it.
It is possible to buy a replacement switch board (which contains two switches, one for detecting that the screen is out and the other that the screen is tilted up). This saves some fiddly soldering (you still need to solder 3 wires), but costs a bit more (around $27 I recall).
If you replace the switch board, be very careful to ensure that the wires don't get tangled in the gears, and that the board is precisely placed. My board was not level with the chassis, only by about 0.5mm at one end, but that was enough to cause the lower switch (that detects whether the screen is tilted) not to activate.
Good luck!