I received a postcard a couple of days ago from Air Vent (since I was at the seminar last year), but there was no mention of the buck knife; but after registering, one gets this message:
Ask the Expert™ Seminar Registration
Why a seminar about attic ventilation? | Locations and Dates | Registration Form
Thank you for registering for the Air Vent Attic Ventilation: Ask the Expert seminar.
This confirms that you have registered for your preferred Air Vent seminar.
You should also receive a confirmation shortly at the email address you supplied. These will be the only forms of confirmation you receive from us.
And, as a thank you for attending this seminar you will receive a Buck Knife (while supplies last).
We will see you there!
So I guess the buck knives are still available.