Bleg!

My favorite Merchant O'Death has asked for my assistance, and I'm passing on the request:

I have a friend who is looking for an AR barrel (NOT an upper) chambered in 5.45X39, that also has the PROPER BORE DIAMETER. He recently purchased an AR in 5.45 and after a trip to the range (and a 16" group at 100yds) discovered that, while the chamber is 5.45, the bore diameter is 5.56mm. I figured you might have an answer or two. I would greatly appreciate any info you are willing to pass along.

I couldn't find anything in stock anywhere. Any ideas?