Pair of black vinyl windscreen "A" post pillar covers. Special order, lead time required.
From the manufacturer:
99% of all Minis had painted "A" post pillars in body colour. We have developed a kit (pair) that fits exactly in this space with the least amount of fitting. A fibreboard panel covered in black vinyl material has double sided tape on the reverse side. This piece is adhered to the "A" post and a flap on the outer side is held in place by the door seal on the post.
Simply peel the tape off the double sided tape, place, turn over the body flange and replace the rubber door seal.