Perhaps they are now only servicing the whole motor assembly which might go for $843.
Supposedly, Hardinge is in a bit of a bind with some of the "legacy" Bridgeport service support. WHen Hardinge bought out the assets of the defunct Bridgeport Machines, not all of the tech info was in readily available and/or useable condition.
Hence, a lot of the old service parts info (specs, part numbers, sources, etc) weren't useable, current or even verified - some might content that they supposedly wanted some of the old legacy stuff to fade away - the sooner the better. You don't make money selling brushes for old machines, only selling all new CNC machines.
Apparently and supposedly still, Hardinge bought the assets to get access to the classic mill and really didn't plan or even care to "support" the balance of what Bridgeport hath wrought. May it RIP. THis pretty much leaves the users/owners to have to fend for themselvess.
Not pretty nor what you want to hear but spot on according to my research efforts into servicing my machines.
The most common suspects to contact include EMI as they are run by former Bridgeport engineers - they're servicing a lot of machines and/or some of the softare, especially those that use the BMDC Digital Controller system.
You might try calling BPT Machines (Carol Stream, IL, they do have a web site as I recall). They do a lot of service and are well connnected in the industry at both the supplier and component level.
Production Tools in Michigan sells a lot of aftermarket Bridgeport service parts for the classic mill. Perhaps the motor brush part number is common and they might have some.
Then there is always the internet....
You might even get the info off of the motor and, if it is a commercially produced one (USEM, Reliance, etc), perhaps a motor shop might be of help.
At times like this, your OEM part number list may and probably will not serve you as well as it did back when Bridgeport was one of "the" machine tool suppliers you could count on in the USA.
Any more, Bridgeport is just a name and what used to be a former glorious machine tool supplier is nothing more than a masthead/marketing facade when it comes to legacy hardware.