Just got a email from the local Honda dealership- part number 11394-333-306, a cb350f head gasket, is a discontinued part. On top of the three weeks I've waited to find this out, I could either (a) wait until they get back to me to tell me that they can't source any from another dealership, or (b) buy an aftermarket gasket.
I think I recall seeing a Yoshimura head gasket for $150- a little pricey. Anybody else used an aftermarket product with good luck???