Leica or Canon LTM rangefinders are about the smallest rangefinders I know of, and unless you intend to use Leica lenses the lenses can be pretty affordable, use the FSU Ltm lenses and great, I have induster folding leica copy lens on my leica IIIf which cost me peanuts, and is great, s Komura 80 mm lems again cost peanuts and good lens, an old Canon 135 and an Jupiter 35mm lens, all great lenses, buy a body and get a lenses, or the other tiny camera I use is the Werramat, terrific camera and with 2 extra lens, a 35mm and a 100, both made by Carl Zeiss, Can't really help with SR's as I haven't used one for many
Richard