I'd go with SA's Custom Shop or John Harrison
http://www.harrisoncustom.com/Home.aspx
John offers Ionbond and can work in smaller jobs like sights/finishes with good turnaround times.
ETA - SA charges $300 for IB, if you use Novak they charge $300 I believe but you'll also pay the shipping fees from their shop to whoever does IB.
Quoted:
I think Springfield Armory provides Melonite if you ask for it (they have to for their XD line) and I think Novak has the Black Diamond finish, which I believe is IONBond.
SA will NOT do Melonite on 1911's. I asked Dave in the CS about it and he gave me a pretty good reason why not. The main reason was the high temps involved.
Novak can send a pistol off for IB, but they do not offer it as a standard finish. NHC offers the DB, which is IB.