Picked up a trickle charger and charged for 2 hrs.
Bike started, let it idle in driveway for 45 mins and then took it out for a scoot to test out the new TRE and get fuel
Everything IS working, battery is back to a full charge, but I think I'll keep the bike hooked to the trickle charger every couple of weeks.
Thankfully the charger came with a hookup to keep wired to the battery with a quick connect, so it's an easier hookup than having to take the seat off every time.
The charger has an auto cycle that turns the unit off once the battery's charged.
I'm thinking you're right, that since the aux unit does not have a switch, there will still be a steady draw from the communicator - so better to keep the battery charged than taking chances - especially as it gets colder.
Thanks all for the help.