I wish there were a magical solution. We have had elderly dogs and have found the options for dog diapers lacking. Good luck.
To make sure your dog's diapers and inserts will fit correctly, measure your dog before making a purchase and be sure that the inserts are designed for the pants or diapers. If you've forgotten to buy inserts for your female dog in heat, you can also use pads designed for human women. These absorb fluids so that you don't have leaks. Sanitary pants and inserts for female dogs are also good protection for your pet after an operation.
I’m sure it’s difficult with a giant breed. I know that Barkertime XXL sized diapers list dogs up to 130 pounds. They’re expensive but washable. There are also several people on Etsy that make washable diapers. I think they and Barkertime would be willing to help you with a custom fit. I hope that you’ll find something suitable to help you with your Newfie–they are such magnificent creatures.
Dog Diapers...for old dogs...or stubborn ones
When reviewing different types of diapers for dogs, consider:
Have you considered learning to "express" your dog? Vets do it all the time and can show you how. It entails squeezing your dog's bladder until she empties it. You do it three times a day and then won't need the diapers. I dont know all the circumstances of your situation but this is a common solution for dogs as they get older. I have a cat with neurological damage that we do this for.Ensure the diaper is comfortable and doesn't cause irritation on the dog's skin. Take a dog for a short walk and notice if the diaper causes any discomfort while walking. If the diaper is ill-fitting and it causes discomfort, the dog will want to remove it.Dog diapers are recommended for puppies to avoid accidents in the house, dogs traveling for an extended period of time, female dogs in heat or senior dogs that have urinary incontinence. With diapers, you don't have to clean after your pet and you may also allow it to sit on the couch without worrying that your dog soils it. Certain dogs don't like wearing diapers and they try to remove them by dragging their body on the floor, rubbing against furniture or chewing and tearing the diaper. Train your pet to wear diapers using positive reinforcement and by discouraging it to chew or remove the diaper.Dog urine marking occurs when a male or female dog pees in small amounts around various locations either outside or inside a house. Dogs often mark as a way to communicate with each other, and it is especially common in households with multiple dogs. Studies have shown that it is tied to dominance and pack status behavior. It is not always a training issue, but our P-Suits® can stop this behavior immediately while you look into training options.