DC Offset Blocker/Killer - where to buy in the USA

   I have McIntosh MC8207, the first unit I bought from an authorized dealer came with a loud buzzing coming from the left transformer, and was replaced with a new unit which came with even a louder buzzing. The buzzing can be heard from 8 feet away. Then I was told to have install new 20 amp outlet that has its own isolated grounding.
   That was done professionally by an electrician who installed two isolated 20 amp outlets, two 20 amp circuit breakers, two copper polls for grounding for each outlet, each outlet has its own neutral and power line. After all this done the buzzing sound was still there.
   I was then told to buy a power conditioner which I did (Audio Quest Niagara) which was like $4000 and that did not help. Called back McIntosh and was told that I might have DC offset in my AC line and was told by McIntosh that I would need a DC Offset Blocker/Killer to which when I asked them where to buy one they told me to go on the internet and search to find one, to which I cannot find one.
  This bothers me a little bit, if you as a company think that I have dc in my ac and i need a dc blocker wouldn't you need to sell one as well. I brought this amp to my friends house and it was the same no improvement, so my guess is that he has dc in the ac line as well.
   So If anyone of you knows where to buy a DC Offset Blocker/killer please let me know, but even if this helps kill the buzzing wouldn't you guys think that this expensive somewhat hifi amp/brand should be silent from the factory. I mean this is two units in a row all purchased brand new.

My house is 5 years old, everything is brand new, the whole neighborhood is about 8-9 years old, my electrician says that I have perfect power coming to the house and everything looks fine.

Thank You

I did buy it from a big cash flow dealer but that doesn't meant they would want to refund it, we will see how it all plays out next Tuesday. Also I am not trying to return everything I am just trying to get an amp that works that's all, but dealer and McIntosh are saying that it's me with the problem and not them which makes it more difficult for me to return it for a refund or another exchange.
I had same problem with my amps due to DC offset in the AC.  I tried AVA DC blocker. It did work, but the bass dynamics became restricted, and sound was lifeless.  I couldn’t live with those compromises.  Van Alstine tried to convince me it was all in my head. Ha! I bought Gigawatt power conditioner with built in DC blocker. Problem solved with no limitations of the AVA dc blocker.  It’s on the expensive side though. 
“Sounds like they are jerking you off with no happy ending.”  Stereo5

Sounds like you’re speaking from experience. Lol!
What about trying a 3000 microfarad 200v non polar cap in series with your line to block dc if there is any. Also if the line cord is flipped over (left prong on the right) shouldn’t the buzz move to the other transformer?
Otherwise I’d think you should be able to see the offset at the box with a VOM. 
IMO you have a faulty unit that Mcintosh should replace.  
If its the amp, it should also buzz/hum at the dealer’s store. Sounds simple enough to verify.