\ Something extremely simple like this cageless ring-only design, but with sharp spikes. I dont want to stop him from masturbating, but I want it to hurt. I have found some with screw in spikes, but I dont want them to be removable. Let me know if this exists, or if it can be made.
You could get the adjustable one that you like then once you have the setting that you want use the red locktite on it. That would require heat from a flame to get it apart. You can be sure that he would not do that
goto aliexpress and type spike cage I bought this one: https://www.aliexpress.com/item/4001227639816.html
Rigid chastity has that exact thing. http://rigidchastity.com/index.php?route=product/product&path=64&product_id=54
We have this one from Hot Steel Toys. https://hotsteeltoys.com/ktb-chastity-device.html Very effective once its locked on.