Hi Auntie,
Go to a sports shop that sells footballs and ask them for a football adaptor........it will fit a bicycle tyre pump and your fenders will be at your mercy.
I've managed to blow up fenders quite easily without an adaptor. Just press the end of the hose hard against the fender whilst you pump. Fenders shouldn't be rock hard - if they are slightly soft, they spread the loads much better.
Altenatively, Anchor Marine and Polyform both make fender adapters for their products - try a Google UK search.