I recommend these two rangefinders:

Canon QL17 Giii 35mm rangefinder with 40mm lens

Minolta Hi-Matic 9 35mm rangefinder with 45mm lens

Neither needs batteries for operation. Batteries are only needed for the built-in light meter.

Both are small, quiet, unobtrusive, capable of producing high-quality images, and inexpensive.

http://www.flickr.com/photos/11336821@N00/5227629588/