"We sure it was video that killed the radio star...?"
The Sprinter Custom "Popstar" is part of the Custom Weapons Program run by Sakura Gunworks. Unfortunately, only 3 of the 15 "Popstar" submachine guns were completed before the company experienced unrecoverable financial hardship.
If you can find a "Popstar" in the wild, first scan the barcode plate inlayed on the side of the gun to check legitimacy. If its real, prepare to spend a fortune, or fight like hell to pick one up.