Ribbon cable are really pain to repair as they require too much hard work and really good concentration to repair as they are delicate ... that why i use to break them when doing some electronic project.
Recently i broke ribbon cable of my apple mighty mouse and i searched all Ebay for that spare part but no luck i couldn't find a single part , especially in india it's too difficult to get all these stuff.
But you see necessity is the mother of all invention , i did't invent this process but luckily i did repaired my ribbon cable.
Procedure Goes here:
To repair ribbon cable, expose the ends of the ribbon wires. Fine sandpaper (say 600 grade) usually achieves this is , but personally i used a fine razor blade.
"You only need to abrade about 1-2mm of the insulation for this and only on ONE side of the ribbon. Check with a continuity checker and a couple of sharp pins that you really have access to the wire.
"Use a piece of flexible adhesive tape Stick this on the back of the broken cable (i.e the side you DIDN't abrade), aligning the broken pieces as closely as possible.
"Next you take another two pieces of tape and you put them over the TOP of the ribbon cable so they wrap round to the tape underneath, but leaving a small gap at the point where the exposed wires are.
"Finally we are ready to bridge the broken cables. This is done with conductive epoxy resin. Silver-loaded resin can be purchased from specialist electronic stores. It is not cheap but cheaper than a new gadget, for sure, or more easier u can use fine point conductive pen and overcoat pen you can buy them from SUMITRON
I am attaching few pics so that u can get fair idea how it should be done.