As said before, folding cameras will probably do the trick.
For portable, good quality MF there's the Mamiya 6 and 7, but these are still quite expensive, but there's a whole lot of good folders out there from brands such as Voigtlander, Kodak, Agfa and Zeiss.
Because of the Voigtlander Bessa III, I've seen people asking ridicuolously high prices for Bessa I and II, they're not worth that much compared to the fact that they sell the Perkeo models (also Voigtlander) for something around 50-100 dollars (maybe even cheaper if you get an extra good deal). Another good thing about folders is that they're sometimes available at flea markets and second hand stores, unlike Hasselblads and Mamiyas that are usually sold directly by their previous owners (at least that's my experience up here in Norway/Sweden).