Call around to a few of the big yards and see if they have some take-offs or know someone who does. Likewise, Stabilized Marine in Ft Lauderdale, very knowledgeable and do a lot of service and upgrade work. Stabilized Marine Home
Sailorman in FtL and Marine Connection Liquidators in Ft Pierce are also worth a call.
In each case you need to tell them your model# to make sure the shafts mate correctly to the fin.