FMA 4Q Rotating Shotgun Shell Holder (Model: CAM870)

"I've tried almost all of the 4Q shotgun shell holders sold on Evike, and this is the only one that reliably holds TM870 shells in a skirmish.

Since you're only loading one shell at a time, there's no need for the shells to come off as easily as they do on other, less complete holders. Highly recommend getting these specific models, especially since they're cheaper than the other FMA options.