Chris,
Call AVEMCO, I recall them issuing a press release around the time of
Oshkosh covering this with little additional policy cost (for incidental
instruction). Don't know how this works for primary where the student will
use the plane solo. Good luck.

wrote ...
I'm a CFI, and am considering buying a Cherokee, mostly for personal
use. I would like to be able to offer occasional flight instruction in
that plane (less than 50 hours per year). This would consist mostly of
BFRs and intro flights. I recall seeing that insurance for such
occasional instruction was offered somewhere, but I can't seem to find
it. I don't want to pay an extra $2000 for such coverage tho. Is
anyone else doing this, and if so where did you obtain the appropriate
insurance coverage?