Ebay or Gumtree are good places to look, hone your searches for local area and collection only and there are some nice bargains to be had - if you see one thats further afield Shipley can sometimes be very helpful and efficient.
and check the current that it uses - my 95k has a 500w motor that has made it a complicated mistake really.
Having said that there are some good and compact servo motors on ebay if you can only get the head or the motor looks dangerous.
good luck and please share your progress/hunt!