I thought he'd kicked the bucket. He used to have a huge collection of 60's and 70's 2 strokes.
Go see a exhaust maker and see what they can whip up. Surely there's a motorcycle after market exhaust manufacturer in the States. There used to be about a dozen of them just in Australia.
When I was a young bloke a lot of people ran Dunstall and Wassell aftermarket muflers. They didn't look as good as Conti but they were a fraction of the price. Call a British bike specialist, there's a few of them in America.
Then there's the Indians. They're making shit loads of pommie replica gear. Someone on here years ago bought one of their alloy Imola tanks but I never followed up the result.
Or you could just buy some Conti pipes from the Ducati Vintage Store. About a $1000 US + postage.
Marmitte Conti