Why not buy Wahoo’s Trackr Radar?
It seems to work equally well (I can tell for certain soon), but has much better battery life (essentially double if you put both on low steady light, 15 hours vs. 8 hours, 67 % longer on high steady, 10 hours instead of 6 hours).
I recently lost my Varia that I was very happy with — except when it comes to battery life.