Odometer

Hi lads and lasses the speedo on my 90 works and the trip recorder works but the odometer does not work I bought the car off a dealer who said it had a 100000 miles on after buying found out it was stuck after contacting the x owner it probably has about 120000 miles on it and has been bust for a while any ideas if this can be fixed or is it a new speedo.
Thanks.

Mine trip died on the speedo, it is sealed with ring of metal crimped on-best buy another