Novices and newbies discussion

I’m struggling to find the right ring size. Here is this cage

I have a small 40mm ring and a medium one at 45mm. The small one feels too tight and uncomfortable to wear. With the medium ring, I can keep it on all day without many issues, though it doesn’t feel very secure when soft. Does anyone know how to adjust a ring’s size? Is it possible to get custom rings even if you don’t buy a full custom cage?