Have you thought of using asynchronous serial? This adds a start bit and stop bit to your data bytes so you are sending 100 kbps but the hardware supports a bit rate of 115200 so that will work. This will use the serial hardware so you can't use it for stuff like Serial Monitor unless you have an Arduino MEGA with multiple hardware serial ports or the Leonardo which use USB directly for communication with a PC and has a hardware serial port to spare.