I know the wire isn't serviced separately. It comes with a new shifter dial indicator and is light blue. Cost is about $50.
If you want the factory repair you buy the new dial and use an old speedo cable or similar to snake the new wire it down your steering column to the connection under the dash. If the broken wire is accessible, attach the new wire to the old and pull it through the column to the connection under the dash.
Or...you can use a wire connector to repair the broken wire. I assume you knew this already and wouldn't have to ask if that were the case. So your wire must be broken off inside the column. You can repair the wire after pulling it through the column from under the dash. Either way you'll have to fish the repaired wire through the column.
I'm sure you'll get a few more suggestions.