Mini PCIe Cellular Modem
https://shop.solid-run.com/product-category/accessories-services/?filter_wifi=lte
https://source.sierrawireless.com/devices/mc-series/mc7354/#sthash.oX3VquMa.dpbs
https://www.quectel.com/product/lte-ec25-e-minipcie
https://techship.com/products/ Here are some cellular modules that can be used for mini PCIe interfaces: