+1 vote for slipping a 6x9 folder in the bag, and some rolls of chrome 120.
I toured Grand Canyon & area last summer, with four cameras in three different formats, and it was fun! But that was for landscapes. They tend not to run away while you decide which body and lens to use 😀
The 6x9 (a Nettar, btw) came to me last minute for the trip, I barely had time to check the focus, and good thing I did, it was off by 1/2 turn. I did however forget the tripod adapter at home.
As a result, I have sunrise shots of the Grand Canyon that are handheld with a 105 mm lens, not as sharp as they could be, but even so 6x9 slides are something else. Works out to about $1.25 a shot at US prices for film + dev, but it's really worth it.