fluidtransferproducts.com’s menu isn’t populated under automotive, but it did initially look promising. I hadn’t gotten around to checking VW parts, but Apogee’s link had 14 mm stud length brake nuts, PN BQ4511LT, which should do the trick. The brake nuts I have only have 12 mm stud length, which leaves only 1 mm compression. Maybe OK, maybe not.
I thought about milling the boss’s down, but sucessfully clamping the work down and preventing contamination when the chips started flying seemed daunting.
I found a website that sells the 14 mm stud length:
http://www.brakeconnect.com/product/brake-line-fitting-male-m10-x-1mm-316-long-thread
So, I’ll try them. Thanks, all!