Mine failed half way into our tour of France on the way to the Le Mans Classic last month!
I followed the instructions on the Pelican website and mended it myself, buying the replacement gear from Odometer in the US.
IF you do it yourself don't follow all the Pelican instructions, you don't need to remove any of the screws on the rear of the speedo; lever up the bezel, pull off the needle, take out the two screws holding the face on, and you will see 4 screws that hold the Odometer and Trip mechanism to the base assembly. Taking these 4 screws out, you can lift off the mechanism, dismantle it and replace the broken gear.
The hardest part is taking off the needle.
Good luck.
PHilip