I am going to echo the suggestion of the Fuji GA series. I have one and it really is pretty much a point and shoot camera. In size it feels like a mid-range SLR with a pancake lens attached. In operation I can work with it about as fast as I can work with a 35mm compact, though with the benefit of a high quality lens, large negative, and accurate auto exposure.
My one and only complaint about the GA series is the fact that the lenses are relatively slow. If I could open it up to say f/3.5 I would consider it perfect.
It is easily my go to travel camera.
The Fuji GF670 has AE but no AF. It's very compact when folded and shoots 6x7.
Fuji GA645 is the one. Over the years, I've had a broad variety of MF's, from Zeiss 645/6X9 folders, Rollei's, Hassy's, Mamiya 7's. Still have Rollei & M645 Pro, but I use the Fuji more often. Hard for me to find fault with it.
I have both Pentax and Fuji.
The Fuji GA645zi is the lightest, but of course the zoom lens is fixed on the camera. Think "point & shoot on massive steroids." It weighs 2 pounds, and is quite compact. A 52mm filter fits on the lens. Aperture and shutter speed can be manually set, but it's manually zone focused. It would have been utterly awsome if it was a real rangefinder too, though.
The Pentax weighs four pounds with 75mm lens, and is slightly bulkier. The interchangeable lens makes it a much more versatile camera. I feel much more comfortable changing the film, as the Fuji has the rear element exposed, while the shutter is between you and the lens with the Pentax.
If weight is the most important factor, use a Holga. At 8oz, nothing beats it yet. For quality of the image, I can't find fault with either the Pentax or the Fuji. The lenses on both are superb.
As other already have mentioned: Fuji GA645Zi. The point-and-shoot of MFs. Don't let that description fool you into thinking it is anything of a toy. It has excellently sharp optics and the auto focus never misses (well not more than I do with manual focussing anyway). In short, a very nice camera, with larger than average negatives (645 is about three times the area of 35 mm film).