Pet rescue is a good place for finding rescues of all kinds of dogs, and all kinds of shelters. There are some vet practices that also list dogs/puppies and I'd consider asking around the local vets in your area if they know of any "accidents" looking for homes. It is unlikely you'd find exactly a dog like the one you had before. Where did you get him originally? Maybe there would be some more there. Otherwise, you should check out Pablo - that I and Emma linked.
Kennel cough is very common in places where lots of dogs live together, especially ones that have been rescued from bad conditions. It's a bit like a cold, most dogs get over it in a couple of weeks, and there are vaccinations to help prevent common strains. So I wouldn't let that put you off.
RSPCA / AWL usually have a kind of quarantine area for new dogs, though it's no guarantee. Both places, but especially AWL often have puppies that never get listed on the websites. It can be hard to tell what a puppy is before it grows up. Some litters have more than one father. So while the owners might know one of the fathers, they might have missed one. Not sure how a kelpie x and a bc x could be confused.
I find it hard to believe that the dog came from a rescue with worms, a place like that should be reported. Makes me wonder if it was really a puppy farm in disguise.
When you find something that looks promising - post a link here and we can check it for signs of dodginess if you like. Or ask the RSPCA to check the link if you want somewhere more independent.