Hi Violetta, and Welcome to the Great American Roadtrip Forum.
My first reaction to your request is that in this day and age it would be hard to get anyone to carry a parcel for a stranger. Not that this is a 'flight type' security issue, but most folk would be hesitant in case they were pulled over, and illegal items were to be found in the parcel.
I know you mean well, but that may be something to consider. If this were me, I would welcome a carrier to watch me pack the parcel and inspect each item if desired. If you ever watch any of these cop shows on tv, you will understand that saying you are just carrying something for another, simply is not an acceptable explanation.
Good luck.
Lifey