There are many options here and we are using a custom setup. However previously we have used the PepWave devices and they performed well. Pepwave Max HD4 can carry 8 simcars, 4 active and 4 as backup.
FYI they had some issues recently: https://thehackernews.com/2018/08/mikrotik-router-hacking.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+TheHackersNews+(The+Hackers+News+-+Security+Blog)&_m=3n.009a.1800.bt0ao0dj2y.13nw
“Security researchers have discovered at least three massive malware campaigns exploiting hundreds of thousands of unpatched MikroTik routers to secretly install cryptocurrency miners on computers connected to them.
In all, the malware campaigns have compromised more than 210,000 routers from Latvian network hardware provider Mikrotik across the world, with the number still increasing as of writing.
The hackers have been exploiting a known vulnerability in the Winbox component of MikroTik routers that was discovered in April this year and patched within a day of its discovery, which once again shows people’s carelessness in applying security patches on time.”