As suggested earlier, a baby crown graphic could be a good choice. Here are some weights for comparison:
2 by 3 Crown Graphic, 65-mm lens with Grafamatic holder (6 shots, sheet film) 3.0 lbs 1.36 kg
2 by 3 Crown Graphic, 65-mm lens with Horseman 6 by 9 roll film back (8 shots) 3.125 lbs 1.42 kg
Voigtlander Bessa II 2.125 lbs 0.96 kg
Nikon F with Photomic T finder and 50 mm f1.4 lens 3.0 lbs 1.36 kg
Nikon F3 with 45-mm pancake lens 2.125 lbs 0.96 kg
Rollei 35S 0.78 lbs 0.35 kg
The Crown Graphics are relatively cheap. The roll film back adds some bulk, but the 120 film is cheaper than sheet film ($1.37 per shot of 2 by 3 roll versus $3 per shot 2 by 3 sheet). The roll film back gives a little bit bigger negative. The 65- to 100-mm lenses are all quite small. The 90 mm is slightly wide, and for 6 by 9, similar to a 40-mm lens on a 35-mm camera. An 80-mm may be ideal for you (equal to a 35-mm lens on a 35-mm camera). The 65-mm lens on 6 by 9 is close to a 28-mm lens on a 35 mm camera.
A downside to the graphic is that with wider lenses (< 75 mm) the sport finder cannot be extended and used at infinity, and small viewfinders for 65-mm or wider are harder to find. Usually, I use a Graflex finder on top of the camera for a 90-mm lens and imagine the rest beyond it. I don't use a rangefinder. The wider lenses need to be stopped down around f11 or so, anyway, so zone focusing is not that difficult. A homemade distance scale can be fastened to the standard's rail for wide lenses (the cameras usually have one for a 100-mm lens already).
I am pretty sure I get better resolution with the 2 by 3 than a 35 mm. I often take my baby graphic on mountain trips with lots of hiking/easy climbing. I switched to it from the Voigtlander because the Bessa viewfinder is so small and the lens and bellows blocks some of the view. It's much handier to carry though. I use an old army canteen holder on my belt.
More important than the weight, I think, is the ergonomics. The Crown Graphics take some getting used to. I wouldn't bother with the 35-mm adapter spools. Keep it simple.
I would add in a Mamiya 7 & 80mm lens, which comes in at 1210g (2.6lbs). Cost aside, it’s surely the benchmark against which other options are judged in regard to the OP’s desired spec.
The optics are a match for anything for starters. Its weight is competitive, and although not as compact as a folder, it’s quite ergonomic & hand holdable. Other cameras might be 200 grams lighter, but may be fiddly. The 7 is a well laid out conventional camera body (okay maybe the 150/210 w/ separate finder not)
It’s also got its own 35mm pano inserts, which are not after market, and the pano adaptor works well. And unlike many of the other options on the table it has six different lens options to choose from. Oh and it’s actually a 6x7 as the OP specified.
The downside is it’s electronic (but so is almost every device I use) and therefore hypothetically can be hard to repair, but then again ever tried to repair a modern €2500 Mac?
The cost of the Mamiya 7ii is high, but comparable to a high end dslr. As an owner of both versions, I think the original Mamiya 7 is just as good as the 7ii at a significant discount.
I’ve traveled widely with a Mamiya 7 for 17 years, and combined with a light monopod and medium speed film it’s an incredibly portable and high quality photographic tool.
This is a fun thread with lots of great solutions. It’s ultimately about finding the right combination of cost of ownership / picture quality / functionality for one’s needs.