So you're using the HPX500, which has a 2/3" image sensor and a B4 lens mount...
To mount a Nikon lens on the HPX500 you need a B4 to Nikon mount adaptor. However, using the Nikons this way won't change the depth of field characteristics of the camera's sensor. It should also be noted that 35mm lenses have a narrower field of view when mounted on cameras with 2/3" sensors than they do on 35mm cameras (i.e. your Nikons will act like longer lenses on the HPX500 than they do on your SLR).
If what you're after is "35mm depth of field" then you'll need the PRO35. You didn't specify whether you own the Cooke lenses you mentioned or whether you'd be renting them - I assume renting? If this is the case and money is a concern then perhaps you could buy/rent a PRO35 with a Nikon lens mount and use it with your Nikon lenses instead, sparing yourself the cost of renting the Cookes.
A couple of things to consider:-
- Depth of field adaptors like the PRO35 absorb light. I don't know how much light because I've never used one, but I think I recall reading that it's typically about a stop to a stop-and-a-half. Perhaps someone else can correct me.
- It's harder to pull focus on a lens designed for still photography (like your Nikons) than it is on a lens designed for motion picture photography (like the Cookes).
Apologies if I'm telling you anything you already knew. Good luck with the film.