Ok, good thing you made me check. I stand corrected. The Concentra arms would fit on the motor just fine, however their design causes them to rub on the housing, which I didn't anticipate. It's SO close to turning freely, it just barely rubs in a few spots. I was also incorrect about the blades, the originals will not fit on any of the new Hunter/Casablanca arms as the Eastern Shore uses the older pattern.
So, you can do as suggested above and find a fan with a 2xxxx model number and take parts from it, or I'm trying to find you an arm with a design that might work for your fan. It's kind of a shot in the dark now, I really hadn't noticed that little difference in design until now and I'm seeing a LOT of Hunter fans utilize it. This from the Beachcomber looks like it MIGHT work, and you could also grab a set of blades that are basically like the originals, but would have the right spacing. Blade sets are pricy though, if you're not set on the bead board you could get a standard set from another model for much cheaper. www.hunterfan.com/Replacement-Parts?ModelNumber=53122 I'm looking at the Sontera as well, which is basically the same thing with a different light and standard blades. Getting a better look, I do think these arms from this model or the Beachcomber are a good bet. They're structured more like the older arms. There are also standard blades here available for only $25 if you don't want to pay so much for the bead board ones. Just trying to provide all the options. www.hunterfan.com/Replacement-Parts?ModelNumber=53114