You must have a key maker in town! That's how we did it, went by, left the keys ( one ) there and then selected a corresponding ornamental blank. Key makers have a huge catalog and making them is very cheap. Depending on the blank between 20-30 euros. You get a very good quality and you can also have the same engravings, etc. attached.
@That Punk Ass is being modest. He has wonderful Shapeways options for a variety of locks https://www.shapeways.com/shops/chastegoods See also https://www.chastitymansion.com/forums/index.php?threads/customchastity-device-key-options.52235/
We went for one of these, took about 5 weeks to arrive, the quality is amazing and KH loves it, they seem to have semi regular discounts I think we got 10-20% off, they are a hand made item, they come with a quality genuine Burg lock and an emergency spare key in a wax sealed display case which is nice but yeah they are still not cheap: https://www.chastity-shop.com/colle.../products/silver-heart-key-with-cylinder-lock There are also a few cheaper but still nice options: https://www.aliexpress.com/item/1005006490665020.html https://www.aliexpress.com/item/1005005853378290.html https://www.aliexpress.us/item/1005005849965415.html