On amazon there is a stuffed toy that has the sound of a heartbeat. Has good reviews people say it calms puppies, worth a try?

SmartPetLove Snuggle Puppy Heartbeat Stuffed Toy for Dogs - Pet Anxiety Relief and Calming Aid

https://www.amazon.com/SmartPetLove-Snuggle-Puppy-Behavioral-Golden/dp/B000S753WK