What is the ruling on delaying prayer due to being busy shopping for necessities or being on a means of transportation, when there is someone who refuses to go to prayer and wishes to postpone it?

It is recommended to be diligent in performing congregational prayers with the mosque community. If there are preoccupations, there is no harm in delaying the prayer to perform it congregationally with companions, and that is sufficient to lift the sin according to most of those who hold the congregational prayer to be obligatory, even if it means missing the superiority of praying in the mosque.

However, if you will be praying alone: it is permissible to forgo congregational prayer if you fear harm to property or family, or missing a companionship or a significant interest; otherwise, it is not.

Delaying the prayer until its time expires is not permissible merely for the aforementioned preoccupations.

You should invite your companions to maintain prayer within its prescribed time and explain the virtue of congregational prayer.