You can achieve this easily with a managed L3 switch, or 2 managed routers. Look up first hop redundancy protocols, specifically vrrp if you want to go with a non cisco managed switch. The switch must support vrf if implementing this solution - basically you need both isp routers to provide the network in the same subnet, on different ports on the switch. The 2 ports on the same switch will be segmented by vrf, and loop across from one vrf to the other. Set up vrrp between the 2 vrf and set up tracking reachability on the primary vrf. You can tweak timers if you want too, but I’d leave them at a few seconds at least for the track to go down and implement a vrrp decrement. Point the default gateway on lan to the vrrp vip address for automatic failover and back for the minimal interruptions. Just bear in mind that these are enterprise grade switches and solutions so cost might be prohibitive, especially in a lower income country. Also you will need to support these technologies so would be good to know what you’re doing as it’s a complex setup. There are other solutions possible, but then again they would rely on other enterprise grade equipment and technologies that you may or may not have access to, and are also going to be cost prohibitive. For a simpler solution, you could look into a consumer grade dual wan router, but I’m not sure if they exist or are any good. Best of luck