Another USB-WWAN (mini-PCIe) adapter from fleabay. Cost about 5€, so no big risk.
I have a Huawei ME909s-120 3G/4G/LTE modem working fine on one (Ubuntu/Mint NetworkManager/ModemManager integration works perfectly out of the box!), but the USB-miniPCIe/WWAN adapter I have has an AMS1117 LDO (5V to 3.3V at max. 800mA) that gets hotter than I'd like, and there is no way to add heatsinking to it. I'm hoping the new one has a buck converter instead. Can't see the text on the 6-pin chip, but the presence of an inductor (and some capacitors) indicates I can have hope.. although what you get off fleabay isn't always what's on the pictures.
I'd rather not have to make the adapter board myself: soldering the mini-PCIe connector is at the brittle edge of my current skill. Otherwise it is very simple, just USB, a SIM card holder, mini-PCIe connector, and 5V to 3.3V regulation, and some supply bypass caps.