Do a quick search on the net and you will find lots of sites on autoharps and some luthiers that can help you. You will also find an autoharp e-maillist that can help lots.
You will have to decide whether you want a chromatic that plays several keys, or a diatonic which has a bigger sound but will require one harp per chord. There is lots of discussion on this.
Harps are easily found on e-Bay but you really need to hear them to know what you are buying.
I use diatonic and have 5 harps, plus some junkers.
Good luck
Richard Wright