Why not the PB-6? The issue might be no electronics pass-through, but if you are using a reversed enlarger lens or some such with physical aperture ring, that's fine.
Novoflex does make or used to make (aBay) a Canon mount electronic pass-through, pretty expensive, as all Novoflex things are. There are Chinese knockoff electronic pass-through gadgets out there, stick one end on lens mount, add your favorite adapter and bellows, add other end of pass-through gadget (connected to the first by a curly cord) to Canon EF lens, stick lens onto bellows. I have no idea if it works well or at all, I have just seen the ads.