And if you're not filthy-rich, a Minolta Autocord, Yashicamat or Mamiya C220. The latter is a bit bigger but has interchangeable lenses. Lots of good 645 SLRs are pretty portable too and might suit your shooting better than a TLR.
Originally Posted by JLP
If you really are filthy-rich, the ultimate portable+quality MF travel camera is probably the Mamiya 7.
Personally I take my RZ67 with me on big trips. I can fit a good 3-lens system in my backpack with a bunch of film and don't need to compromise on quality when I'm in the places where I'm likely to get my best shots.