Coming late to this thread, but just did a bunch of research on these for a reader:

Several out-of date harps could be fixed up and used.

Stupid-looking but practical:

OS Guitarro can be held like a guitar, due to a scissor-like      leverage mechanism that allows the buttons to be placed on the outside edge of the instrument. Could be played in something like upright position. Hard to come by in playable or restorable condition, without spending real money.

Chromaharp Chromalin (Chromaharp's less successful, but
cheaper version of the Guitarro) Really made for holding "upright" I have one of these that needs fixed up, but I'm sure it could easily be played by short-armed people.

Oscar Schmidt 10 Sierra, a child-sized 10-chorder that an inventive person could probably add a couple chord bars to by cannibalizing a 12-chorder's combs and custom-building two chord bars.

Or, if you want to go stat of the art and have the money: the D'aigle Sparrowharp P.S. My reader ordered a Sparrowharp and is deliriously happy with it.

Paul Race