Ghost Recon Breakpoint, extended magazine for SASG 12 located?

Does anyone know where or how to acquire the extended magazine for the SASG 12 shotgun?


You need to buy it from Marias Shop. At the Attachments Tab (the one with the gun and the quarter gearwheel) there must be the extended magazine for the Shotgun, which is the one for the SASG 12 too.

The one which is highlighted in the image is the right one.