So, I have the same problem with my 3ds. and I after much research, I think I finally found the part... http://www.newark.com/molex/501461-0401/...
this is for the whole part that the touchpad ribbon cable goes into, and while I certainly don't need the whole part, it's $1.08 on this site, and I can just pull the retaining flap off.
I know there's no picture, but I found it through molex.com . See this site here for an image.
Note: I am going to order this, and see if it really IS the right part. I will be back to let you know! :)
Just stopping by to verify. I received the 6 that I ordered from newark, and they indeed ARE the correct part.
They are VERY tough to get back in. I found it helps to raise the upper contacts using a small flathead screwdriver, so you can get the piece on easier. I broke 1 out of the 4 upper contacts while trying to put it back on... although, I still got the part on the remaining 3, and my 3ds touchscreen still works with no problems. After getting it on the upper contacts, I could rotate the flap closed like normal, and it snapped in nicely, and holds the touchpad ribbon tight.
Note: I ordered 6, and broke 3 before the 4th worked! So, yes, order extra! they're tiny little flaps.
From what i've noticed, my NDS Lite uses the same connector for the touchpad, so I assumed the other models would as well.