I just got one of these from a friend, it's really clever and seems secure.. D'Addario Auto Lock. Nice material, too. It works over all the types of pin that I have, from Dunlop Dual Design, Gotoh and Schaller, even the type for Schaller locks, which I hate.
https://www.amazon.co.uk/DAddario-Accessories-Guitar-Strap-50BAL04/dp/B07SSJYHYJ