Just for reference, here in Australia, the following two MiFi units can often be purchased for about $25AUD (with at least 4GB of data) on special at the supermarket. They’re both locked to Telco but can both be unlocked via code from Ebay for a couple of $$s.
Optus 4G Wifi Modem ( Alcatel MW41CL/ Alcatel Linkzone)
Telstra 4GX Wifi Modem ( ZTE MT910Z)
Because they’re both hostless modems they just plug in via USB and show up as tethered. A little bit of “overkill” as they are actually full routers within themselves (though limited in their functionality) but the good thing is that because they have their own internal battery you don’t have to worry about overloading the USB port. On one of my old TP-Link routers, if I try and run the Alcatel without a battery it just keeps rebooting as the USB port doesn’t supply enough juice.
If they work with the Mango hopefully they should work with other GL.iNet units as well (Will probably in the position to verify on some other units in the very near future )
I know at least the Alcatel unit is available on T-Mobile in the US but unsure if other country telco’s support these units as well, but I’m sure they’re out there.
Hopefully of use to someone somewhere out there