Hi Ray, done some checking for you,Things you will need to check-out. Firstly he drive in the later KN models is shorter in length by approx 5mm , this is very important with the KN7 as there is only just room in the case for the short drive I am not sure if the length of drive is so critical with a KN6500 the Two drives I have found that work in the KN7 are the Alps DF354H(121G) or the SONY MPF 920 These should work in the KN6500 however NO warenty,
I don't what the Ebay prices are like in Australia, good refreb units sell for about 10/15.00 GBP so are worth trying as they wont break the bank.
Hope this helps your friend Regards John.