I went a bit crazy in sainsburys yesterday - they do three flavoured still waters with malic acid - cranberry and raspberry, apple and blackberry and peach. 70p per 1.5ltr, not on offer at the moment.
They also do a flavoured sparkling water strawberry and kiwi which has malic acid but that has apple juice in it so not sure if its ok? might post on the 'what can you drink' thread and ask.