For an expedition tour: 2x11 SRAM GX mountain drivetrain. They sell a version of their 11 speed cassette that works on regular freehubs. Microshift sells a bar end shifter that works with SRAM 11 speed rear derailleurs. Then for the front shifter, you can just buy any old friction bar end shifter. On my own bike I use an old Shimano front shifter that I scrounged from the local bike recycler.
I'm also an advocate of touring on a 12 speed 1X, but it seems that others here are not willing to give up the high side of the gear range.