Here's what you do. Collins or the avionics shops want something ridiculous like $300/each for the digits, so just buy an old radio as a spare and pinch from that. You can get an entire radio for less. All the numbers are the same except for the first one (even between the NAV and the COM), so they're interchangeable. It's really easy to swap yourself - done it many times.
Slide the unit out, unscrew the lock screws for the tuner knobs, pull them off and just remove the front. Now you have easy access to the digits. Just pull the broken one out and replace with a new one. Make sure the pins are straight so they go into the sockets. You can slide unit in and turn it on without without putting front back on, so you know it works before it all gets put back together.
