All Kink3d base ring 0 too big. Options?

My boy measures 36mm diameter. We got the smallest ring kink3d does but the cage still slips down the shaft after a while.

Would getting an XD ring rather than a standard help with this? Or are there other cobra-compatible 36mm rings (must be plastic/silicone)? Or is there any safe way we can alter the ring?

We don't want to change the cage or use a strap if there are other options. Thanks.

 

Thanks. I was looking for a lower-cost option. I don't object to him buying a new ring, but he's on a budget. I can re-sell standard rings on reddit, but not custom ones if it's still not right. I think the issue might be gap size (36mm is without putting a finger underneath), which is why I wondered if the XD might be a good option.