i think there available but ive not seen them in a shop and thats a lockable lead so that you can leave your dog outside a shop without fear of it being pinched,also i find it hard to get practical sensible(no pink bows!) coats etc in really big dog sizes?hope this helps ,sounds like a brilliant idea,good luck
lots of dog clothes, animal feeders that put a controlled amount of food in the bowl with a touch of your dog/cat’s paw,and obstacle course sets for guinea pigs