A jar of locally-produced white honey makes for a great souvenir. They sell nice hand-made candles too.
Official website http://www.volcanoislandhoney.com/
Phone +1 808 775 1000
Address 46-3694 Pu'aono Road, Honokaa, HI 96727, USA
Coordinates 20°3'21.898" N -155°29'21.535" E