I have a half dozen different 10rnd tube carriers made for stock class play.
A couple are vests with tubes in front, most are harnesses around the waist.
Some of the harness types are also capless.
So I've tried a few different makes & models.
In the end, the simplest and least expensive option is still the shotgun belt that you can buy at Sports Authority for under $10. And these tend to run large, I have touble making them small enough to fit a 32" waist.
Anything else is a matter of style & what you like, and what you can afford.
My personal favorite was custom made in black leather, but I spent $120 on it.
But one thing you should have is what they call a "dump pouch".
This is just a bag easy to throw used tubes or 12gs in so you don't waste time trying to fit them back into a harness.
Mine came from an automotive store, it's supposed to be a small trash container that hangs behind the front seat. It has an elastic mouth on top, and velcro holding the bottom closed. The strap that would hold it over the car seat I run through my belt and let it dangle.