In article <4rreqs$9om@newsstand.cit.cornell.edu>, mm15@cornell.edu says...

>I have been looking for a polarizer filter to be used on a Nikon SB-24 (or 25
>or 26) to filter the light. Optical quality is not necessary but good color
>balance (It must be neutral) is important. I hoped to find an inexpensive
>rectangular plastic filter that is easy to mount or cut but even the Cokin
>brand polarizers seem to be round filters mounted inside the square holder so
>they can be rotated. Rotation is not important to me; and the polarizer can
>be either a circular or a linear type optically. Edmund's "Technical
>Specification Polarizing Film" is the only one I have found but I am not sure
>how neutral it is (compared to a good glass filter) and it seems they sell by
>the sheet only at about $ 85. Suggestions are welcome; thanks for your help.

Why not just tape on a cheap used 72mm glass filter (I have several....),
which you can check for color neutrality by placing it on a white sheet
of paper.
Hope This Helps