For the SK35, you have several good solutions for a polarizer.
Lee makes a 105mm thin CL-PL, which fits perfectly. It's a bit on the warm side, but a nice filter.
B+W makes a 105mm normal thickness, which fits very well also, and is a bit cool.
Heliopan makes a 105mm very thick CL-PL and by it self is to my eye neutral.
The bigger issue you will find is looking for a ND filter (if you need them).
The only 105mm I know of is my Hitech, in the Firecrest line. I waited over 1 year to get 2 of them. They are excellent filters, no color cast and thin, so you can easily stack 2 if needed.
Other option is the Lee SW-150 with a Lee wide angle ring. This is much heavier solution, but the lens can support it. The SW-150 will take 2 filters in the 2mm thickness. I have a Nisi CL-PL and 2 of the Firecrest ND filters all in the 150mm size. But since I finally got the 105mm ND filters I rarely use the Lee SW-150 now.
Paul Caldwell