GSM Module

I am reaching out today for some assistance regarding a sitation with my DELTA 3. According to the product documentation, it has a slot for an M2 GSM module. My intention is to expand its functionality by incorporating this module. However, I am finding it challenging to locate a place to purchase this module online.

So, I am wondering if anyone else here has encountered this issue or has had any experience with this. Could someone point me in the right direction where I can find a compatible GSM module for the M2 slot of the DELTA 3? I would greatly appreciate any suggestions for online retailers or even specific model recommendations.

I am looking forward to leveraging the collective wisdom of this community. Thank you in advance for your help!