Itead Raspberry Pi 3 Model B+ plus SIM800 GSM/GPRS Module Add-on V2.0 also for Raspberry pi 3 also - AliExpress
Add cellular connectivity to your Raspberry Pi
Add cellular connectivity to your Raspberry Pi
Connect Raspberry Pi to cellular data network — The MagPi magazine
Raspberry Pi 4G/LTE Modem Kit - Sixfab
SIM7600G-H 4G HAT (B) For Raspberry Pi, LTE Cat-4 4G / 3G / 2G Support, GNSS
SIM8262E-M2 5G HAT - kit with 5G module SIM8262E-M2 for Raspberry Pi - Kamami on-line store
Raspberry Pi SixFab IoT Gateway Quickstart - Hackster.io
Modem LTE/3g /2g with raspberry pi 3/4 A+/B+... - Hackster.io
Raspberry Pi Sim Card Add-On Provides Mobile Connectivity | eTeknix
Cap HAT GSM / GPRS / GNSS / Bluetooth for Botland - Robotic Shop
Get Started with Super SIM, the Raspberry Pi 4 and the Sixfab Base Hat | Twilio
4G HAT for Raspberry Pi - LTE Cat-4/3G/2G with GNSS Positioning | The Pi Hut
Connecting in Lockdown — Raspberry Pi Zoom Box | Medium
How to connect your Raspberry Pi to a 3G network | The Pi Hut
Tutorial - Using Cellular Modems with the Raspberry Pi 4B - SwitchDoc Labs Blog
Build an IVR System to make Automated Phone calls and send Messages using Raspberry Pi and SIM800L
How to Connect Raspberry Pi to Internet using GSM SIM800L Module?
Amazon.com: 4G / 3G / GNSS HAT Module for Raspberry Pi Zero/Zero W/Zero WH/2B/3B/3B+/4B/Jetson Nano, Based on SIM7600A-H , 4G Communication and GNSS Positioning Module Support LTE CAT4 up to 150Mbps :
Using 4G LTE wireless modems on a Raspberry Pi | Jeff Geerling