I looked around on the web for 10 minutes or so. I thought Novoflex might have something. I went through a huge listing of their offerings but didn't see anything for Nikon.
I did not look through the Fotodiox site--they would be a potential source for an adapter; they DO SELL the Nikon F lens adapter to Canon EF mount adapter for around a hundred dollars; I own one, it is their deluxe adapter, and it has a manually, hand-operated mechanical controlling system that sets the Nikon G-=series lenses to one of seven different closely click-tabbed aperture sizes. The settings are unmarked, and I just count the clicks. Of course, the back end of that is a CANON mount. Since you're using it on a bellows, perhaps there could also be a second adapter added, Canon EOS to Nikon F, to mate to the front of the bellows.
Used with a G-series lens mounted in reverse, the Fotodiox G-series adapter would control the lens's iris from the very front of the rig.
If you really need a bellows, then you need a bellows. The Kenko AF tubes, set of three, control f/stop and keep AF and keep EXIF reporting and TTL control using Nikkor G-series lenses, so that would be one option. It's a three-ring set with something like 13mm, 20mm, and 36mm tubes, so it does offer quite a lot of extension, but it is, of course, not as flexible as a bellows.