I second the Bontrager rear light. a couple of years ago i saw some dudes with wicked bright rear lights during the day, and wondered what were those. Did some research and found that the Bontis were the best deal out there. They sync to the Garmin unit, are rather inexpensive (but not cheap), and have decent battery time, say, 10 hours approx. The best part is those lights are super visible during day time (I call them them “daytime lights”), and I have noticed a significant difference in the way cars approach me - well, they actually see me now. I don’t leave the house without that light. Best part is you can check its battery charge on the Garmin unit, and it communicates when the light is running low on juice. Totally worth it for a 1/3 of Garmin Varia price.