My friend's rudder failed and Foss (then still in Florida) offered to modify a similar stock rudder to replace it.
Extensive delays, missed dates, phone calls unanswered, AND the rudder they shipped did not match the specified dimensions, so it had to go back to them and the whole cycle started again.
I have no idea if Foss relocated to CA or if someone bought them out, but I'd hire a Kentucky Whittler to hand carve a rudder before I'd send anyone else to Foss. They came highly recommended, but totally fell down on the job, multiple times, with no apology or compensation.
The Goudgeon/West Systems (epoxy) folks mentioned someone up in Maine who does custom CAD contouring of foam blocks, then builds them up into rudders. You might try contacting them for a referral.