I would suggest contacting the breed club and they can put you in touch with nearby breeders, you may have to travel a bit and also wait for the right puppy from the right breeder.
Please do make sure the pup is kc reg, there is no good reason not to and chances are non kc will not come from health tested parents which is also a must. The breed club should have info on their website regarding what tests need to be done.
https://www.portuguesewaterdogs.org.ukHealth tests appear to be a fair few which should ne done.
https://www.portuguesewaterdogs.org.uk/health-conditions