The Hohner Piano 26, 27, or 32. The shorter ones (26 and 27) are slightly easier to handle. Of course, to hold them against your body requires that you do not use the handle on the back, but rather hold them at the bottom (end opposite the mouthpiece).
These models are no longer in production but you can buy them pretty readily on Ebay and other auction sites for roughly $30 to $80 dollars.
Note that Hohner makes several models loosely referred to as Piano 26s and Piano 27s. The one with the sound holes on the back look like this: