Used one of these for a few years to inflate my Ribcraft and now the Zodiac, does a great job and only needs topping off with the foot pump. The large fitting wedges into the neck of the valve, if you push and twist the valve to hold it open it does an even better job (have to be quick to close it though)
http://www.aldi.co.uk/uk/html/offers/2827_10049.htm