If I am not mistaken the very first Leica was made for the purpose of testing b&w negative motion picture film. Because of sensitivity variations between emulsion batches, testing was essential to avoid surprises when the film was developed. Leica made their own brass cartridges for loading ( and reloading over and over ) cine film before Kodak introduced pre-packaged "135" film in 1935. And don't forget the 1936 first Exakta model was called the Kine Exakta. The difference in the sprocket shape is of no consequence as far as I can determine. In the 60's it was common to purchase motion picture film in a variety of emulsions in bulk from Freestyle and other mail order retailers.
Unfortunately, I believe that RGB Color has just closed due to an unreasonable leasing agreement. Business was good, but they couldn't come up with the increased rent money. I am in the process of looking for movie labs willing to take up the slack though. I'll keep everybody informed. One can still obtain slide prints from negatives (although only C-41 or already-processed ECN-2 I believe) through a lab in Florida, forget the name right now. I'll let you know when I think of it.
I think the florida lab is Dale labs (http://www.dalelabs.com/) but i might be wrong....
BTW if you look at the Kodak Professional web site, click on "cinematography," you'll find in their collection a white paper on why doing this is a bad idea.
YMMV of course - Kodak has a financial interest in your decision. But their issues cited were the same as the ones I mentioned earlier.