it shouldn't cost too much to get a new speedo cable
I picked up a complete cluster with a speedo cable from my local wreakers for $30, and installing a speedo cable isn't very hard.
Its just a matter of pluging up 1 end into the back of the cluster
then feeding the cable through the casing then pluging the squarish shaped end into the speed thingy of the gearbox (takes about 5min to do