This one prop maker named Mike is amazing. Though if you want to order from him, do it now! He's so good, he's always overbooked~
http://fantasyprops.com/I bought the Witch Hunter Robin pendant from him and it looks so good! I always get complimented on it and I love it ^_^.
And if Mike is too busy to make the arm, try Limebarb~
http://www.limebarb.com/Though once again, order early, as they are also booked out months in advanced.
Also, though I don't know what your budget is, expect to pay a pretty penny for your Ed arm, as Mike and Limebarb aren't exactly cheap. Their quality and accuracy is excellent, but you pay for that extra detail. I paid $35 for my Robin pendant and it's just a chunk of resin plastic. Though I love it nonetheless ^_^.