[gchappel]

Unless you have a complete aversion to the computer- photoshop can easily replicate almost any filter. You may have to stack a couple of images- but much easier and faster in the field than a filter.
Polarizing filters are about the only one you cannot match later. It can darken skies and take the shine off of water, leaves, etc. But be careful- it can look artificial, and also give a weird gradient in the sky.
Save your money- get better at photoshop.
Gary