I have only seen one ENO before but I would have that a standard siz snake skin, like listed on Just Jeff's site
of the JRB site
would work fine. I made some oversized skins to hold my HH and an under quilt . All I did was to increase the measurement on the wide end of the fabric from 13-14" to 18" and it turned out great.
Hand sewing a snake skin would take a long time. Snake skins were my second sewing project and it really doesn't get any easier than sewing skins. Maybe your Mom can help you get started.