Fitting a CPL filter to an s95/s100

I have a 49mm circular polarizer filter I want to use with my s95. With no modifications, the only way to do that is to hold it in front of the lens with my left hand - not really ideal.

I am thinking that I could use a 35.5mm-49mm step-up ring fitted over the outside of the s95's lens to hold it in place. I may have to add a few shims of thick tape to get it to fit snugly, but ultimately this set-up could still fall right off the front if I'm not careful.

Has anyone done something like this? What was your solution? Is it possible to add a permanent filter thread to this camera?