FYI, the Lowepro Protactic 450 AW II bag easily fit my 645n kit, with much room to spare. The kit includes the Pentax 645n body with A 75mm lens attached, A 45mm wide angel, FA 45-85 walk-around zoom, FA 200mm telephoto, A 80-160mm zoom telephoto, and A 120mm macro lens. Also my Pentax AF360FGZ flash, and a set of Polaroid close up filters. Still have open sections to hold extra film, batteries, and some more lenses if I eventually get them (wouldn't mind getting the A 35mm wide and the 300mm telephoto). I left the very top section open for miscellaneous gear, snack, etc., and put the camera in through one of the side pockets, so it sits near the bottom of the bag. I didn't like the way a camera with this shape would fit entering through the top, also I don't like putting so much weight in the top of the bag. I could probably fit my Sony A6000 in the bag in the other side pocket if I want to carry a digital body. Might not fit my K70 the way I have it set up, but I could probably fit it in with some reconfiguration.
---------- Post added 02-17-20 at 09:50 PM ----------
My first color test roll with the 645n kit, especially with the macro lens. I'm quite pleased with the handling and performance of the camera and lenses.
Pentax 645n (1997) test, Kodak Portra 400 | Flickr