I know there are other bag carrier designs floating around on Thingiverse. This is my take on the design. I designed it to incorporate the curves to fit the hand better and allow for a more comfortable grip. The hooks are also designed to facilitate hooking the bags on.

Three sizes are included to allow you to find a better fit for yourself. The differences are subtle but noticeable.

I recommend printing this at 0.1mm layer height as I found that at 0.2mm with PLA, the ridges from the prints are still cutting into the hand making it uncomfortable especially with a heavy load. If you print at 0.2mm, it is recommended to post-process the print to smooth out the ridges at where the hand hold it for a more comfortable grip. I'm not sure other materials that are less rigid than PLA (say, PETG) would do better. If you try, do post your comments and results.