Lights

If you have a Spesh saddle with SWAT mounts, there are some 3d printed mounts out there https://www.shapeways.com/product/G97897XDT/exposure-blaze-swat-mount?optionId=145139524&li=marketplace looks like no adustment though - can't gurantee it'll point into drivers faces.

"It will only fit round seatposts, though, so if you have an aero model you'll need to buy the specific clamp from Exposure."

I have one with the standard mount on my Sl7 'aero' seat post. The issue with said 'aero' seat post is the back is flat. So neither this nor the standard one are technically suitable. With that said, it stayed put over some fairly dodgy terrain without issue. Obviously the rubber stretch job has enough friction to stop it twisting.
Can confirm that the Blaze Mk3 is suitable in your face. I like the 'braking' function too with all the fancy accelerometer stuff built in.

And thanks @spinnnout I do have a Speech saddle. This will be perfect to avoid the aforementioned bodge.