What is this called?

[wondabar]

I have just bought a swimsuit but need to have something more secure to hold up the bra area. The photo shows the circled metal loop thing with two little balls at either end and the picture drawn shows what it looks like. Basically the little balls at the top are too small which means the metal thing then comes out. I'm wanting to buy a similar metal thing with bigger balls so that it stays up properly. Does anyone know what these are called?

Could you maybe put in a few stitches at the top near the balls, to make the gap smaller, so that the metal bit doesn't come out?

Bra separator bull ring apparently...
https://haberdasheryfan.com/products/5cm-metal-bull-ring

https://www.etsy.com/uk/listing/1578418987/metal-ring-separator-clothing-tops

I could try to stitch the top @RockaLock
@PoachedScrambledBoiledFried well found. However I can't find anything like those on Amazon or EBay. I wonder if there is another term for them?

A few more comes up when I search "u ring buckle" on etsy but nothing on amazon.