You want to be searching specifically for ball stretchers. They’re to all intents and purposes the same as a cock ring but are deeper and usually a narrower diameter.
but you can get a wide variety of them elsewhere. I particularly like steel ones as you get both the stretch from the size and the added weight.
If you do go that route there are usually two types, magnetic and screwed ( ie they’re made in two halfs and you fasten them together ). The magnet types are convenient and seemingly cheaper to make, but they don’t reliably stay together and having a large lump of metal falling on your toe or your tiled floor isn’t great. So I prefer the screwed variety.
Depending on how sensitive he is, he may want to watch the weight at first. The big ones can become uncomfortable, but even the smaller ones can make you feel like you’ve the balls of an ox. And that is a strange but delightful sensation .. for both of you.
I will second the recommendation from @I_ll_try_anything on the Oxballs Ball Stretcher. It’s thick and chunky, stretches well to allow to put on, and then restricts back with some really decent weight to it.
My other recommendation is that when I’m in the mood for some serious ball play I really enjoy layering multiple silicone rings on and around the balls to put more stretch and pressure on that. You can use a variety of rings stacked kind of like you see of the African tribes that do neck stretching, but it’s rings on balls. Or put on a squishy ball stretcher and put a tighter cockring around the stretcher to add extra compression.
