I emailed Andrew Pimental at Jibetech about some Finn parts and he let me know he makes rudders. I think he may be the only Finn builder in the US.
White finish rudders are 400
Carbon finish rudders are 500
The rudders have a ‘socket’ style head that takes a 1.5″ aluminum tube. You can buy these anywhere cheaply.
He said he also has an insert to do the head like the Devoti style rudders.