TacStar Shotgun Rail Mount with SideSaddle, Fits Remington 870, 1100, 1187, Black Finish 1081035, UPC :751103010358
Amazon.com : Monstrum Side Mounted 12 Gauge Shotgun Shell Holder with Picatinny Rail Mount for Drilled and Tapped Remington 870 Model Receivers : Sports & Outdoors
SureShell® Polymer Carrier For Remington 870/1100/1187 (12-GA)