I didnt want to add a cover to mine diffuse because depending on the cover it can also makes it less bright. To make mine more diffuser like, I bought some extra lenses ($3/10ea) and played with scuffing them up. An ultrafine sanding block (sponge actually) does a great job of 'fogging' the lens. Someone makes actual optics that will convert the light to an almost 180 degree 'band' of light but it costs 3x the amount of the light and while I think it is the right diameter, I think it is too thick to fit.

I do very much like the hard mount.

I've recently set this light aside however in favor of the PDW Danger Zone. Twice as bright as a PBSF (1W vs .5) with much, much better off-axis visibility and a very eye catching blink pattern. Do avoid the Radbot though - it is very big and basically half a Danger Zone with a reflector. At the risk of hijacking (not my intent), most places sell the DZ for $32 to $40 - check around, I found them for $20 at Outside Outfitters.

I now have the DZ mounted on the road side seat stay and the PBSF on the other with a Radbot on the seat bag. The Ultrafire is still brighter than any of these but also pretty big.