Tim,
Custom Steel Fabricators in Columbia, TN builds a number of 300 series stainless vessels and high nickel alloy fabrications. Contact Tony Sciotto, pronounced "showtoe". I do not know if they perform the passivation on site or send it out. I am sure they have a contact or know of someone.Telephone number:931-388-6524. Also, DynaSteel in Memphis may be able to help. Telephone 901-358-6231, ask for Charlie Vance.
John Folk