Any online marketplace if you search for the keywords mouthpiece snoring. Warning, as you will see in the reviews, that wearing a poorly fitted one for extended

Any online marketplace if you search for the keywords mouthpiece snoring. Warning, as you will see in the reviews, that wearing a poorly fitted one for extended periods of time will affect your bite since it does dislocate your jaw. YMMV but that should explain why a proper qualified dentist can make you a fitted one for $1k