Hmm... I recall seeing metal cone air filter adapters for sale somewhere on the web.

It might have been the K&N website or one of the other air filter mfgs. I don't know if these other adapters are compatible, but I think they were intended for the same purpose - to connect the tube and filter together.

I have to head out to my office, I won't be able to confirm this until later tonight. If anyone cares to dig through the K&N website, send up a report so I'll know I was or wasn't hallucinating.