Yeah most filters come in all sizes.
Step up rings are about 10-15 at stalls, if u buy from mass order forum can be as cheap as 8 bucks. Most professional grade lens will be at 77mm so step up all you're non 77 lens to 77, can share filters with all lens u have. (unless u go buy 84mm ...)
http://en.wikipedia.org/wiki/Photographic_filter
haha.. never looked up on wiki on filters before though im a wikipedian. deepen my 'craving' for polariser after looking at those pics.
ok... so say i goes to PP and hunt for it, any pointers for me to avoid getting scammed (what are the common scamming tactics there)? And which are the reputable shops there?