I've had good luck when calling Beretta directly. they may not have the parts you want listed on the webstore, but if you call customer service, they can get you any part you need.
my 92FS was so well used, that one day it finally broke the locking block (the thing that hangs down below the barrel and locks the barrel into the slide) I called Beretta customer service and they took my credit card right over the phone and mailed one to me. I had it in about 3 days.
I'm sure you could make a list of the parts you want and place the order through customer service. just tell them you have a inox/stainless weapon that you're replacing the parts on.
Hmm....I don't know if Beretta has the parts you want anymore or not...
I just looked online and saw that their Inox models have black accessories on them:
but when they first came out, they were ALL silver:
Hopefully they haven't "streamlined production costs" and only make black accessories now leaving you high and dry if you have one of the older models of the inox pistols....but it would not surprise me if they did. it's cheaper to make a million of the same part in black, than it is to make 500,000 in black and 500,000 in silver/stainless finish
IF Beretta can't help you, maybe you can find a GOOD gunsmith who can take your stock parts and machine them all down a few thousandths, then nickel plate them for you? I have a 1911 that started out as a stainless model, but it's been nickel and gold plated, yet all the parts still fit together, so the guy who did the work knew how much to remove before the plating process and still have the parts fit together.
There are a few places you can get them. Try brownells.com. they are the official parts dealer for Beretta USA. If they don't have what you are looking for you can always try the Berettaforum.net. they have a good classified section where you can find most of the stuff you need.
That is where I found the control parts I added to this black 92FS.