try e bay for your pump
I would be careful about thinking of a ram pomp, I doubt if you own both
banks of the stream and you need to put a dam across the stream to use a ram
pump also you need to have an abstraction licence to draw water.
If its not to far from your house why not use a submersible pond pump, take
it out when not in use,

--
David Hill
Abacus nurseries
www.abacus-nurseries.co.uk