hmmm. i'm assuming this is a budget music vid and they don't have the $ to rent the downconverter?
if not, and you're getting full rate, why not just find a rental company on your own and rent it personally, then
include it with your invoice.
or...if it's a smaller budget shoot that just doesn't have the money and the cable going down the post is an
issue, attach the monitor onto the camera and look off it there.
or you can shoot blind. i've had to do this once on an arri 3 gig with fried video tap. we we're wide the entire night,
and the footage turned out great.
good luck