I printed 2 of the other auto trash bag hooks I found here on Thingiverse. Both of them broke. I don't know if it is a limitation of my printer or material but I decided to design my own using the strength of the orientation of the printing process to enhance the hooks capability. I'd suggest printing each part in the orientation that I have in the OpenSCAD screenshots.

Neither of the other hooks properly fit my vehicle which is the reason that I decided to go with links. You can print as many or a few as needed to fit your vehicle and they conform to the seat.

I had some of the commercial wire hooks but found the wind could blow the grocery bag out of the hooks. This is the reason for the tight fit of the bag hook. Mine won't blow out

Note: You will also need 1/8 inch rod stock of some sort to make the pins for all the links.

E3D BigBox

Doesn't Matter

Yes

0.2mm

30%

After printing the two hook parts (HookA and HookB) for the headrest end you will need to assemble them and glue them. I used acetone since I printed in ABS to fuse them together.

I used 1/8 inch brass rod stock which I happened to have on hand to make the pins. I found that if I ream the center section (left side of the link) with a 1/8 inch bit the fit is still tight enough to hold the pin. For the outer open section (right side of the link) I used a 3.2mm bit which is slightly over 1/8 inch so that the center section holds the pin once inserted but the outer clearance allows the link to swing freely. You could also ream all the holes for clearance and once pinned put a dot of super glue on the outer open sections so that it is the center that moves freely.