Is there a place I could just buy the saline injection for breasts? Can I do the injections myself?

Unless done under sterile conditions with a detailed knowledge of the anatomy, this is not something you should consider after watching a YouTube video. You must also understand that this will only last hours.

Don't do that.  You re apt to harm yourself or at least get lumpy uneven breasts and terrible infections.

Saline is easily available at many pharmacies. However, injecting saline in the breast will only give very temporary enlargement. In the US, saline implants are purchased by physicians, surgery centers, or hospitals, and not by individuals.