Good places to look for base-layer are Craft, Terramar and Karrimor. I get cold easily (low core temp), but I'm fine with medium-weight base layer, as long as I have rain pants (a "shell") over them. I'm still using my old REI Thaw pants over my Terramar Merino Wool ( 30% Merino Wool), but should get a pair of Mountain Hardwear Returnia for this winter, because the water repellency of the Gore-tex is failing. Aerotech Designs offers a "tall" option, that may be a good fit. They will actually custom-make an item for you, at no added expense! https://aerotechdesigns.com/mens-thermal-tights/