Using Can Bus
In my research, I found that the Teensy 4.0 has 3 CAN buses integrated. That's the best deal I can find given that it's only $20 US. Most other solutions I've seen are more for the board that can understand CAN info and the board that can transmit it.
I see there is a CAN bus breakout board for the Teensy 4 - http://skpang.co.uk/catalog/teensy-40-triple-can-board-with-teensy-40-and-28-lcd-p-1576.html - Its a bit expensive so I await a hoped for DroneBot article on the CAN bus before committing my funds.