Used hotspots are $12 on eBay. The Franklin T9 is hackable and fun, but it would be nice to have Ethernet and OpenWRT for less than $100
GL.iNet GL-AR750S-Ext
Wiflyer WE826-T
Installing OpenWRT requires soldering wires to access the serial port, so I haven't bothered yet (the native OS works fine for what I need), but as I understand everything is supported.