Check here: https://click.intel.com/intel-nuc.html?limit=32 Intel® NUC Spare Parts. If you want the skull lid, it is immediately available. They seem to be out of stock on the blank lid; you may have to wait for restocking (click on the Notify Me box to request).
Hope this helps,
P.S. BTW, I deleted your duplicate requests; only one posting is necessary.