Corrective optics for a bike light

[mjbmikeb2]

I have a bike light with a 20 degree acrylic TIR lens. It looks like it is a custom design complete with O ring for waterproofing so substituting another lens is not going to be possible without compromising the water resistance.

How would I go about making or finding a corrective lens which I could stick in front to turn the diverging beam into something more focused?
I see various convex lenses on Ebay/Aliexpress that are designed for flashlight use but I think I need something with less curvature.

 

[lumen aeternum]

20 is pretty narrow - I find its inadequate to light up going into a turn.
I'm looking for something that has LEDs aimed 45 deg left and right, going Turbo when the bike goes into a turn.