lomo slitter
I think this is what you want. I got one from J&C a few years ago, and a second one in a Lomo tank from the UK. Some former Soviet bloc sellers of Lomo tanks and Krasnogorsk movie cameras, etc. have them on offer from time to time. As it so happens, I saw two for sale on eBay a week or two ago for about 9-15 USD, IIRC. I can't find the listings now, but they come up from time to time.
One threads the film into the 16mm slot in the drum and pulls it out the other end - very smooth, very fast, and very even.
Kino, don't feel bad. It took me a while to find mine just now. You wouldn't believe the other lost things I found looking for my slitter.
Cheers,
Clarence