I ride with a newspaperboy bag for the summer.
All cotton, it feels cool and comfortable.
I purchased an eyelet kit from the local fabric store; the kind with a punch and anvil that one hits with a hammer to seat the eyelets.
After a little experimentation, I found the best places to put the eyelets, and I run a bungee from an eyelet on the bag to an eyelet on the chest strap, and this stabilizes the bag just like a Chrome bag's stabilizing underarm/chest strap does.
I carry a ton of stuff.
It sits across my hips in back and doesn't shift.
I feel cool no matter how hot it gets, and I love it.
I'll get someone to take a picture of me riding with it and post it on Saturday.