RE: Ofna Alum servo arms
Yep, and they don't sell bags of the little buggers seperately. I'm lucky in that my Hitec 5745 came with a good aluminum horn.
If you can't locate a vendor for the FG ones maybe IMEX, Integy, or GH have a good solid one.
What brand servo are you fitting it to? I can try searching a couple of distributors over the weekend and if I find some I'll post a few pics with the part numbers.