The paint used for bumper covers have a flex additive added to the paint. Without the additive, the paint will just flake off when the cover flexes. Because these get painted separately from the car body, it causes a slight difference in the paint and rarely does the paint match perfectly.
I do not know of anyone making spray cans that have the flex additive for bumper colors. I am not saying that it does not exist, it is I have not seen it. A body shop would be required to paint the cover with the flex additive in the paint.
You can try these guys out: https://www.automotivetouchup.com/
I have bought paint from them years ago for the Vibe to touch up paint chips. They can also load spray cans with the paint of your choice. I just seen they have this; 12 oz Aerosol Plastic Parts Adhesion Promoter, which may help.