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The Canon PL-C drop-in 52mm CP filter has a clever thumbwheel gizmo that allows you to rotate the CP filter while it's in place. It's the best CP solution, for sure.
The drop-in filter holder for 52mm filters takes 'regular' 52mm threaded, round filters, but the filter can't be rotated while the filter is in the lens. In order to use a 52mm B+W CP filter, you'd have to put it in, see what it's doing, take it out, rotate it a bit, put it back in, and see if it did what you wanted. You might be able to get the correct orientation with a single "through the filter" look, but the extra expense for the PL-C is well worth it, if you actually use a CP filter.
The drop-in 52mm gelatin filter that comes with the lens can be used with any single-layer filter that doesn't need to be rotated. You can get some relatively inexpensive Kodak Wratten Gel filter material (incl. ND and IR), and cut it to shape.