I have a couple polypropylene turtlenecks but I can’t find any replacements that are non-cotton. Actually I found the Terramar thermalator but that’s it. Are there any others? I did buy the landsend silk turtleneck but the neck is a little saggy. I go base layer, turtleneck, mid layer, jacket. Mock-neck doesn’t work for me - I need to go full turtle. What do you do?