D-Link DWM-222 4G LTE USB Adapter @ Matrix Computer Warehouse
This dirt cheap 4G LTE modem on a USB stick can be hacked to run mainline Linux - Liliputing
Amazon.com: Eboxer 4G LTE USB WiFi USB Network Adapter Portable WiFi for Laptop Desktop PC Computer, Wireless WiFi Signal Receiver Modem Stick Mini Hotspot (with WiFi) : Electronics