@Jakob4800 I wrote the name of the bag at the end of my post and the steps to get there. Didn't read it? JK
I used Menyoo, hit F9 to get into the proper spooner mode, and then i typed in bag (you have to try different key words). This allows you to visualize different bags, or objects, without having to spawn them, just preview them. I think the bag came up very quickly and I was able to capture its name. From there you do a search in OpenIV.
If you are now asking about clothing items, you need to find the texture files for your specific model and edit the .ytd which are the texture files. You can probably find tons of tutorials on google.
Actually what you could do is download some clothes mods and look at the instructions - you don't need to install them, just look at the instructions. Depending on whether it is Michael, Franklin, or Trevor (Players 0, 1, 2) you will see where their clothe textures are located. Same for MP male and female.
For example, a baseball cap: