I use �1.99 bags from Tescos in my 29litre Zega panniers and they fit very well. See linky http://www.tesco.com/greenerliving/g...ernatives.page

I know the ladybird image isn't to everyones taste but for less than �4 the pair, who cares! They're good enough for carrying your kit into a hotel and keeps the alu staining off.