I have the stainless steel lanyard ring on both my L2 flashlights [the one that fits over the body with a 'lip' for clipping on your lanyard]
Tried to swop one onto my ultrafire C8 .. but they dont fit!
Marginally too small in diameter .... anyone know if you can buy a slightly larger one for the C8 body?
No-one?? 
Ok ..... i want my C8 on a lanyard around my neck when out walking ... the drilled hole in tailcap for a wrist strap is next to useless for this.
What are my options??
I'd say use a paracord wrap of the main body section with an extra loop for clipping a neck lanyard to. Or devise a way to screw a ring to the light using the current lanyard hole in the tailcap. For example a nut and bolt through it securing one of this type of thing to the tailcap.
Paracord idea good 
however ... did a search and found this http://www.gadgeteers.co.uk/products/nite-ize/gripnclip.htm
Made for AA maglite, but should stretch over a C8 ok 
Warmer to hold too ... nice
Perhaps something like this: https://budgetlightforum.com/t/-/5592