There are not magic devices that can solve this problem on their own just in your house. The only devices that even have a chance of working place a device at your house and a second one in a central data center. They in effect run 2 vpn connections and the box in the data center load balances the connection.
You now have a new problem. Packets will be delivered out of order. Unless the internet connections are very close in latency this out of order will actually cause session to be dropped because the end device think there is packet loss. It also causes massive lag spikes in games. You have to be very lucky that both connection to your house are almost identical and you will still have some minor issues with out of order data.
This method is never cheap, you pay of a hardware device plus a monthly fee for the service provided by the central location. Then because this acts a VPN most video services like netflix will block usage from them.