9v 7W power supply/ adapter - pls see below (Malvern Link WR14)

Hi I am looking for the above adapter for a Casio keyboard that I got from another 'free' website, unfortunately there was no power adapter hence my request. According to the socket at the back I need a 9V adapter (symbols next to it show a + then a C then a -) on the bottom of the unit there is a label which reads DC 9V 7W and AC Adaptor AD-5 socket/ jack size required 2.1mm x 5.5mm. The adaptor doesn't need to be a Casio but one with the correct voltage etc.. Thanks