here's a compiled hex file of the v4.84 firmware
normally I don't like providing compiled firmware but my understanding is the the v4.2 hardware is open source, unlike the 5.x versions. though the firmware source for those also appears to be out on the internet too so in mot sure really what the situation is there. However since you've already gone and built up your board I feel bad for you being that its not easy to get the parts so just unzip the file and program it, its the v4.8.4, you might need to double check to se if there's an update once you have flashed the firmware as I can't remember of the top of my head if there is one or not.
all the best and good luck