You're much better off having someone in the vicinity of the boat machine you new rudder hardware
. As that's the only way to test them out after they're made, & thus know that the fit is correct. Especially since they really need to be tested on the boat, with the boat in the water
for a while. Given that some errors or defects in such parts
or their fit may not be readily apparent without real world testing.
For instance if anything else which connects the rudder to the boat is worn, was shimmed when it was installed, or is out of alignment, etc. Then it'll affect every other piece of hardware
which supports the rudder. And it's better to find out that the fit of some of the hardware needs adjusting, or re-machining, before you're out on the ocean & something important breaks.
And as has already been said, they're custom parts to begin with. Or close enough so that you need to have them made on the spot regardless, as their design may have changed with different hull
numbers of your boat's design. Or the rudder may have changed, etc. These kinds of things are pretty common.
Also, while cost is always a factor, consider this. How expensive is it if you have to get towed in after the rudder breaks? Including; the tow, getting things fixed, the lost
time of everyone onboard, & the people that such an incident spooks?
That said, if you can find a shop that's fluent in corrosion
resistant metal work, but isn't a "marine" machine shop, then the price
will be lower than if you go to someone on the waterfront to have the work done. And it would be wise to at least have them inspect all of the rudder's fittings, not just the one. Even if nothing else is in need of replacing at the moment.
Edit: When I say "locally", or on the waterfront, I'm referring to where the boat's located.
And might you have any other pics of things? Especially as that image doesn't match what comes to mind when one thinks about how rudders on catamarans are connected.