Interesting idea. I haven't seen one sold but haven't done a real search.
The ideal diffuser would have to be a slip over that goes on easily and stays on. Once you find the diameter of flexible plastic or rubber that does this ( a cap pf some type? water bottle cap?) you can adapt not only diffusers but traffic type wands etc..
I'm going to keep my eyes peeled for a home-made but elegant solution. Just for fun.
The TK40 is a nice light but two things would improve it.
a more aggresive knurling and some affordable accessories.
The throw is impressive but it could have been focused even tighter. It seems they were compromising a bit to make the light more useful which was a good compromise. A slip on diffuser of a light this bright would be a nice addition.