There's always a way to improvise something, if you have little mechanical ingenuity. Zip-ties are one of the greatest things ever invented for bike tinkerers (even if they were invented for electricians).
Personally, I've found all seat-post light mounts to be useless, because I always have a seatbag on my bikes. But I've always figured out a way to clip a light on the bag or elsewhere.
There are also lights that mount to the seatstay or chainstay, if you don't insist on having the light centered.
These guys make the absolute brightest light I have ever seen. In broad daylight they are VERY visible. It has a post mount bracket but it is trash. It comes with a long velcro strap and I just put the light under the battery pack and use the strap to put it on the bottom of my saddle bag. Works like a charm.
The DiNotte light is not cheap but as one who has been hit by a car from behind, it is worth it IMO.
If you use another light, a velco like strap to attach it to you saddle bag is dandy. Sure it moves a little side to side when you ride, but so what?
A forum community dedicated to Road Bike owners and enthusiasts. Come join the discussion about bike parts, components, deals, performance, modifications, classifieds, troubleshooting, maintenance, and more!