I may have something for you to protect your D4 LCD. I too have the D4 and have used the Giotto's covers on my D300 and D90 for about 4 years. The cover actually saved the day when my D90 LCD was impacted by an unknown assailant. The cover broke but the LCD came out unscathed.
Actually the Giottos model SP8306 fits the D4 (according to the packaging it is meant for a Canon EOS 450D. The cover is the size of the D4 LCD. Beware of the cover however when you receive it. I bought mine and did not put it on right away and after some time discovered the cover had been broken in the post on it's way to me. I have not yet secured a replacement to my D4 but this particular cover has been sold as the one that is the right size for the D4. Until I have a new unbroken one I cannot be sure that it is actually totally an edge to edge covering. I reason though that is just might be better to have something that is almost exact as compared to having nothing on the LCD for protection. I hated the plastic covers because of how easily they could foul with body oils but these Giotto's covers are wonderful.